I have grabbed my share of womens asses when I was young and no one time was any of them offended or angry. That's how it goes in night life.
At bars and dance clubs? Still rude, but a lot different that say, at work, on the street, at the gym. And I'm sure some of the women you grabbed were offended or angry, but women know that if they show it, they could end up in more danger. It's why so many straight women like going out to the gay dance clubs. They don't get manhandled.
When I was a cute young thing at the gay bars, drunk guys would occasionally grab me inappropriately (as they or I walked by). I quickly learned how to hook their thumb with my thumb and bend it backwards. They learned not to do it again.