Every time the Red Pill is mentioned outside of its own subreddit, it directs traffic there. Some people may click that link, visit TRP once and laugh at it, but others see something that resonates with them and stay. Therefore, TRP's growth can be attributed almost entirely to its detractors.

The Red Pill doesn't recruit members. The Red Pill doesn't advertise. Its members are sent there by people who are hating on it.

edit: let me ask a more pointed question: if you think the Red Pill is a misogynistic hate sub that should be banned from reddit, wouldn't you be better off ignoring it and letting it remain a small corner of the internet that most people will never find in their lives?