Because you are a woman, you can't know what men are like when women aren't around. The brutality and cruelty that men habitually show to each other, even when they are allegedly being friendly, is very hard to take sometimes. Blue collar men are especially cruel to men who they think are stuck up because they have some education. There have even been some cases recently where men have successfully sued other men for harrasment using sexual harrasment laws, even when there was no overt sexual interaction. The fact is, no one should treat anyone the way most men treat each other. This has nothing to do with flirting, but you can be somewhat grateful for the fact that being a woman protects you from this because "real men don't hit girls". It probably doesn't make up for all the other gender-based harrasment, but it is real.