I used to play for our local football clubs pool team. I was the only girl in our team and had no problems playing with the rest of my team (pool, I mean!) and we would all win, fair and square against each other.
Once, when we played an away match against an all male team (as most were) my opponent was obviously not very happy to be playing against the only girl.
Our frame started off well - we both potted 2 or 3 in a row. Then he suddenly started, quite obviously, missing pots and larking about. It got to the point where even his team mates were getting annoyed with his 'misses'. In the end, I said to the ref, if he didn't void the frame and start another (I was technically winning) I would just leave. He set up an new rack and we played the frame again.
It can happen with the same sex too though - some people are just bad losers. It doesn't bother me either way, as long at it has been a good, honest game with fair play, that is the main thing and reason to partake, surely?
P.S. Sorry, I waffled a bit there