From my personal experience(in person), not a single feminist-hating person has had a legitimate reason for it. The most common thing I hear is that "feminists hate men". I think a lot of the hate comes from ignorance alone.

I've had friends bring up feminism as an insult or joke, and asked them why they feel that way about it. After listening to their air-based reason(I saw this "feminist" online who says this bad thing about men), I simply tell them that it wasn't a feminist but a sexist and extremist in some cases.

When I tell them that it's about equality, not women being better than men, they're always surprised. I know at least one person who just assumed feminists were sexists because "feminism sounds like sexism".

At some point I started feeling like the overwhelming majority have no idea what it actually is, and I believe that applies on reddit. We have so many people hating feminism because they base their view of it on the crazy women who get a lot of attention online when they tell us video games should be banned and go into detail about ruining a man's like for simply being male.

The thing is, all that is understandable to a degree. Before I knew what it was, I thought feminists were sexists too. I would see something pop up on reddit or Facebook, and it was some girl introducing herself as a feminist, then saying crazy, hateful, sexist things. I thought the women who wanted to be stay at home moms and take care of their husbands had a good reason to hate feminists and that men should just be against them by default. All feminism was to me for years was some sexist group that were only tolerated the way racist minority groups are. "They're wrong because they're hypocrites but we'll leave them be so we can't be called out for oppressing them."

Basically, there's a lot of misinformation and assumptions being made based off the extreme people who label themselves as one of the group that they're obviously against. The same exact way people just assume bad things about religions and religious people because we have the crazies like Westboro or ISIS, but on a bigger scale because feminism doesn't have the backup in numbers like religion does to spread the good word of feminism.