The reason for this "outburst" is this thesis from the University of Iceland.* And this quote from it:
Therefore, although I believe there is truth to the story in the account of the events, I draw the line with the supernaturally strong warrior Beowulf and the evil mystical beings in the poem; I assume they are fictional and the result of exaggeration.
I do not know what Anna Lind Borgþórsdóttir means by "supernaturally" strong. In Samson's case it was really supernatural strength, one which was taken back from him when he was not performing the ritual of a nasir correctly (like when Delialh cut his hairs). In the cases of Beowulf and Hercules this need not have been so. In Hercules' case it is suggested it was because he was some kind of neo-nephelim ... about as St Thomas Aquinas** understands it:
Objection 6. Further, to beget offspring is a vital act. But this has befallen the angels in their assumed bodies; for it is related: "After the sons of God went in to the daughters of men, and they brought forth children, these are the mighty men of old, men of renown" (Genesis 6:4). Consequently the angels exercised vital functions in their assumed bodies.
Reply to Objection 6. As Augustine says (De Civ. Dei xv): "Many persons affirm that they have had the experience, or have heard from such as have experienced it, that the Satyrs and Fauns, whom the common folk call incubi, have often presented themselves before women, and have sought and procured intercourse with them. Hence it is folly to deny it. But God's holy angels could not fall in such fashion before the deluge. Hence by the sons of God are to be understood the sons of Seth, who were good; while by the daughters of men the Scripture designates those who sprang from the race of Cain. Nor is it to be wondered at that giants should be born of them; for they were not all giants, albeit there were many more before than after the deluge." Still if some are occasionally begotten from demons, it is not from the seed of such demons, nor from their assumed bodies, but from the seed of men taken for the purpose; as when the demon assumes first the form of a woman, and afterwards of a man; just as they take the seed of other things for other generating purposes, as Augustine says (De Trin. ii.), so that the person born is not the child of a demon, but of a man.
Whether St Augustine was right or wrong on Genesis 6 - I think people like Rob Skiba II have done some work showing he was wrong there, and thus possibly on angelic nature as such - nevertheless this leaves a door open for demons making a "cattle breeders' move" with artificial insemination. No such being could have left his own genome to Hercules, but he could have been obliged to help Hercules out on some point, as with strength. Especially as Hercules was probably a Pagan and going to Hell anyway - not for being not a Christian back then, but for being actively an idolater and a proud man.
However, Hercules need not have been stronger than Beowulf. And for Beowulf no such origin is suggested. Therefore the supernatural and if true due to fallen angels part of Hercules direct origin need not be assumed as true, it can have been an interpretation of his superstitious surroundings. As for Beowulf no active Paganism is assumed in the poem either. We cannot know, he may have been Pagan or he may have been - like some pludering Goths further south, such as his uncle Chlochilaicus joined - an Arian. Which in itself is not enough to save from Hell, but in circumstances of ignorance of letters and of scripture and of tradition a bit less directly offensive to God than worshipping Óðin the Goth.
So, I am assuming Beowulf received no demonic help. Even so, even though his strength was not supernatural, the feats he is credited with are limited enough to be true.
As to exaggeration, if Hercules being "son of Zeus" or perhaps of "Teshub" was exaggeration, due to Hercules' strength, rather than real information about how he was begotten (since he had a purely human twin I have problems seing him as the result of demonic insemination, and as a Christian I firmly exclude divine such, such an arrangement seems more likely to be the interpretation of a superstitious culture like his own and that of certain African tribes today, where at birth of twins one is assumed to be of demonic origin), THEN that exaggeration was made out of real information about his strength and his birth as stronger of two twins, directly by the society he lived in. Not by the people retelling the story between his time and that of Hesiod writing Ασπις.
Exaggerations are made by contemporaneous observers not knowing their subject well (which is why Christ made sure to have twelve men and especially three of them around Himself nearly night and day so that exaggeration should be excluded from the Gospels and Tradition) and not by retellers.
Exaggeration strengthens the scene and is done by first teller. Telescoping several stories into one strengthens story line and is done during retelling.
So the fault retellers do more likely is changing settings in order to combine two stories to a better one. I briefly contemplated features from the battle of Kadesh between Hittites and Ramses II (who was not Moses' Pharao) reappearing as features of the Iliad. If so, very general ones about horse drawn wagons in battle. What I did learn from the documentary with Jeremy Irons about that battle is very different from the Trojan War. But perhaps not from the details of every battle in it.
Exaggeration is if not always realistic, at least always within the realm considered realistic by the observers. Witches are not able to take off their heads to wash their hair, but this feature can very well have been attributed to them in Russian lore so that it reappears in a tale of someone recognising someone else as a witch. Because Russians before compulsory schooling and outside Holy Orders and Monasteries thought this was realistic.***
This means the main episodes of a historic character - like Beowulf - will not be the result of exaggeration. They are too much in the eyes of even casual observers to be so. Saying that St Francis came to Narni and cured a lame there is possibly an exaggeration of the number of miraculous cures he did, but I do not think so (Narni is favoured by being the origin of Nerva who did well to St John the Evangelist and of being the town of Sister Lucy and of being the etymology of the Land of Narnia in CSL's novels, so why should it not also have been favoured by a genuine cure made by St Francis?), but that presupposes he did really work some miraculous cures.
The leper cured as soon as St Francis had touched him (when he converted, after he had turned away from him and then considered the leper might be the "disguise" of Him who considers the poor as His own)is not likely to be exaggeration of a leper feeling conforted by the fact of someone not turning away. And the killing of Grendel (which was not a dragon, but a troll) as well as his mother and the dragon who in turn killed him are not likely to be exaggerations for ordinary hunting luck or ordinary hunting accidents. Swimming the Kattegatt is not likely to be an exaggeration for swimming across a bay of lake Vaener. But unlike curing a leper suddenly - which is miraculous even with modern medicine, curing a leper takes close to a year if it is done at all - it need not be supernatural either.
Bpi, Georges Pompidou
First Sunday of Advent
A heroic tale of fact or fiction?
by Anna Lind Borgþórsdóttir
A dissertation called in Icelandic "Ritgerð til B.A. prófs" from "Maí 2012"
What I called University of Iceland is "Háskóli Íslands"
Short link: http://ppt.li/f9
** Summa Theologica, First Part, Question 51. The angels in comparison with bodies, Article 3. Whether the angels exercise functions of life in the bodies assumed?
(S Th, I P, Q 51, A3)
*** If they no longer think so, that is so far good. Does not mean compulsory schooling was over all good. But demons have no such great power over human bodies, though they have sufficient power over appearances, when God allows them to use it, to make it appear so on an occasion. And the powers they do not have, they cannot grant to the witch either. Of course, the new theory the Communists introduced that there are no witches at all because there are no demons at all is not correct either.