This isn't "online" culture, it is simply culture. There has always been a horrible group of folks in culture: What we find acceptable changes over time.
This kind of horrible is limited to online culture, though. People don't troll when talking face to face. If they did, everybody would see they were assholes, and they would suddenly find that nobody wanted to hang out with them anymore.
The US constitution declared slaves as 3/5th of a person. Women couldn't do much without a man until recently. We've tortured folks and the Holocaust was a thing. The crusades were a thing.
On a lesser note, people gossip. They'll have "private" conversations about you while they know you can hear. Stop talking to folks because they think you are lesbian.