Bank robbers don't rob banks because they enjoy robbing banks. Bullys don't bully because "omg wow have you tried bullying it so great".
I'm all with you that bullying sucks, but if you want bullying to stop, you better damn well understand the motivation. If you reach for "they are just evil people", you're not thinking hard enough.
Say you build walkie talkies, and a member of the KKK shows up and says he needs 100 of them because they are rioting in a black neighborhood tonight and need a way to coordinate their plans. Do you say “sure in fact take some for free!” just so you can listen in to understand exactly how they are terrorizing their black neighbors, or do you tell them to fuck off because you don’t want to provide tools to a hate group?
I'd look at fat-people-hate and beat-women subreddits more like bank robberers planning their next attack on a bank, discussing weapons, and having a good time looking at viedos of robberies from the past.
Then you can visit them and tell them "But it's wrong to rob banks, it's not your money and think of the poor people working in the bank, they'll get PTSD".
Or you say "Let's discuss the big underlying systematic problem that is larger than all of us, and makes you rob banks, and how to solve it"
Then you get banned from that subreddit, and the bank robberers continue enjoying robbing banks.