You'll see that a lot at a blackjack table, the best thing to do is move. I've seen people do some really stupid things (split fives instead of doubling down, splitting kings instead of standing pat) and win.
When you go against the basic rules of play (always split 8's for example) then another player will feel you've taken a card that should have been his, or you've taken a card that would have busted out the dealer. Sometimes it can be very frustrating if someone who plays a lot, sees someone who doesn't play that often and make plays that go against the basic rules win, while they keep losing. You're always going to find someone who has something to gripe about, especially when they're losing. If you can't ignore them, then I would suggest you just go to another table, there is nothing you can say that will quiet them down, although chances are you'll run into the same issue at another table as well.
As far as poker playing goes, I don't think I've ever played in a game where every person at the table considered themself an expert and everyone else is stupid. You usually can tell the more experienced players from a novice, an experienced player may offer a comment as to how to better play your hand, even winning a pot, it's possible you could have made more money. it really depends on how friendly the game is. Then there are the people that just like to hear themselves talk. I've seen people call out other players for making a bet that they think is stupid, yet four or five hands later, I'll see them do the exact same thing. You just have to learn to tune people like that out.
