I've had mixed experiences with Group Finder. Some groups are great fun, with people who are genuinely friendly and don't get upset when times get difficult. Then there's been other times where people have thrown their toys out of the cot because of wipeouts or that they just didn't like someone elses playing style.
Ultimately, it's symptamatic of the attitudes of what I hope is a minority in the SWTOR and wider MMO community. They appear to lack any basic social skills or empathy for other people. Now yes, I can understand a bit of frustration if someone isn't the brightest crayon in the box, but that doesn't excuse people being downright nasty towards them. There are perfectly civilized ways to voice your concern/opinion, yet these people seem devoid of any knowledge on how to.
I had one incident last night where the Healer was dishing out advice to everyone, which was ironic given that he wasn't actually doing much healing at all. I bit my tongue and politely acknowledged his feedback, but then later he throw a hissy fit at our DPS and stormed off, leaving our group stranded at the last part of the flashpoint. I toyed with the idea of naming and shaming him when I returned to the fleet, but thought better of it, as it wasn't going to achieve anything other than venting my spleen.
My personal approach to flashpoints is that I'm more than happy to help anyone complete them. If someone is having difficulty understanding what to do, I give them the benefit of the doubt and grin and bear it until they get the hang of things - which usually isn't too long. On the one occasion when I have had to leave, I made a point of politely apologising to the group and trying to part on reasonable terms, rather than getting nasty and personal about their inabiilty to play the game.