The reasoning goes like this:
"There was also a pertinent point about our sitting around "happily eating where animals lie mutilated and dead all around us" - which I'm sure we all do from time to time at social events (although, in my case, not at all "happily" - but, I do sometimes do it). Whereas we wouldn't happily associate with a known rapist at such social events. Should we continue to participate in these events (although it is very hard not to, with dead animals being all around us in society)?"
I think we may attend those events to educate others about Abolitionist veganism and human rights. To educate people in a way so that they understand that what they are doing is wrong - that they are participating in causing unnecessary harm to sentient beings.
I think that it is sad when people attend these events without educating others - just sitting silent when others are participating in animal exploitation. I have also failed here. Everyone has alot to learn.
People are commiting injustices everywhere. We should stand up to stop it. One way to do this is to attend events, and through conversations educating others about what they do is harming and killing animals unnecessarily.
We live in a world where people also express lots of racism and sexism; and people fighting for human rights still attend events where participants are racists and sexists. So in that respect I don't think their point is valid.
The Abolitionists against human slavery attended events were many people attended that were slave owners, etc...