I don't pay too much attention to the friends system, AKA the augmented social networking organ that is typical of any forum. I'd rather just have a few upvotes and positive comments here and there, rather than have everyone like me.
As others have said, blocking is necessary if you want to avoid misery on this site. I know it's a little bit taboo because it's exclusionary and it's akin to taking your ball and going home after losing the first round.
But I don't think there's any honor lost in pulling the plug on someone who just wants to bust your chops for not subscribing to their world views.
Neither do I think it's wrong to block somebody who is just plain annoying because they always make sarcastic and cynical comments. I know that I can be sarcastic and cynical myself, who isn't, but when I block somebody for being this way it's because they do it excessively, and they tend to deliberately misinterpret questions and answers just to derail the topic and gain attention for themselves.
But, of course, nothing is infallible. If someone hates your guts enough, they'll find a way around the safeguards.