With all due respect, Rob, you're falling into that common trap of excusing implausible reactions simply because of the genre.
We accept things like time travel because its a science fiction story and, if we didn't, there wouldn't be a point to the story.
However, that fantasy element doesn't mean that we have to accept when people act implausibly or out of character. People should, for the most part, act plausibly in any situation. Otherwise, the story's internal logic fails.
Let's use the "Back to the Future" film as a comparison, since it also (potentially) involves time travel.
When Marty went back to the 1950s in the time machine, he ended up on a date with his mother. His mother tried to kiss him and got freaked out because he knew it was his mom. A perfectly natural reaction.
But suppose Marty hadn't gotten freaked out. Suppose Marty had been blase about being kissed and pawed by his own mother. Suppose he had thought it was great. Would you have excused that simply because it was a time travel movie? Of course not. You'd have been creeped out, because that isn't how you expect a person to behave in that situation, regardless of how he got there.
Its the same with Lost. They may be on that Island because of some science fiction or fantasy plot device. But they are still on an island and in in danger. And people who are stranded and in danger will, at some point, tend to get pissed off with each other, frustrated and scared.
