Pay attention to "missing steps"
Also, stop being friends with sexist/homophobic/racist people who refuse to be respectful to other people. Some people can't be persuaded to be decent and the best course of action is to avoid them/not invite them to anything. People who doesn't respect other's boundaries shouldn't be offered "another chance". Redemption is not always possible.
So if you notice that the women around you avoid one of your friends, don't wait for them to tell you about him, suspect that he is a "missing step" and stop inviting him to parties. You can met him one on one and keep the friendship without putting women in an uncomfortable position for the sake of "not making a scene" or politeness.