Great points here from several people. I've only really been into airsoft for a couple years so I can't speak on the history of this problem, but I have seen it in a few games I've been at. I know I want the games to play seriously and more realistically so if people are bending or breaking rules I can get frustrated. Maybe that's justified, but I have to take a few things into consideration. I am not everyone else and they might not notice what I notice. Also, maybe they are less "serious" players and more want to have fun rather than follow a series of strict rules (though that's still no excuse for going to an event with rules and breaking them). Hey, maybe I'm actually the one who's wrong and didn't see what I thought I did. People do cheat, but there's also a myriad of possibilities that could put them in the right.
As for the method of just shooting them till they call it, it's really the only way I can see to maturely deal with the situation in-game. If they're angry about being shot more than once then they should realize it's not the shooter's job to confirm the hit. If they don't want to be hit again they have to make sure it is obvious that they're out of suffer the consequences. I know I on occasion hesitate to call hit, not to cheat but just as a "dejected pause". This also prevents things from moving along as smoothly as they should and it's totally my fault if someone keeps shooting me till I yell "Hit!" with some sort of decent clarity.
I'm also not a fan of raising all the fps limits. For one the limits are generally there for safety reasons. Secondly, that creates a disadvantage for people using guns with lower velocities. Some builds legitimately work better (ex. hop-ups) at lower velocities. People can tell well enough if they were hit with the current limits as long as they are paying attention.
But I think in the end, come on, this is just a hobby. We aren't going to die or be seriously injured if someone bends rules. Players aren't losing anything measurable if hits aren't called. The amount of fun you get out of something is really up to you! If something isn't happening properly then a) deal with it calmly and maturely b) avoid the situation in the future, or c) don't let it bother you.
I'm sure I just regurgitated a lot that was already said, but there you have it in my words.