The Question and Answer section for Beowulf is a great resource to ask questions, find answers, and discuss the novel.
During the feast, Hrothgar's thane Unferth tries to discredit Beowulf. He accuses Beowulf of losing a swimming contest with Breca. Beowulf disagreeshe not only defeated Breca, he also fought off heaps of sea-monsters, thanks to both God and Wyrd....
Beowulf rips off Grendel's arm with his bare hands. I'm not sure about the latter part of your question.
I would say insulting.