I'm not really sure I have beef with anyone ,usually the people I don't "like" are just due to just differing personalities or something like that (maybe I find them annoying or something), really minor stuff you know, I don't actually hate the person. In that case, I think that it's nice that they took the time out of their day to make something with my UTAU, so I think I should return the favor and like, repost, comment, etc.
But like I said, off the top of my head, I don't have anyone who I REALLY don't like, it which case I think I'd still want to try and be nice? I try not to be actively rude/mean to people without them messing with me first. I just don't like confrontation, it's my Achilles heel