Men Going Their Own Way. Basically the most extreme form of Men's Rights Activism.
I've heard from both. They really don't share that much. Honestly MRAs have a lot in common with feminists and want to break down gender roles. Red pill guys just are sick of paying for dinner lol. I think on the surface there are some good points, but they get dumb about it. A lot of them kinda use my favorite comic Patrice O'Neal, but bastardized what he said.
Parts of the MRA has been taken over by the repillers. At least, from what I've noticed from the few posts that hit r/all from r/mensrights. ---