Most likely they’re referring to /r/MensLib, which is the subreddit for the Mens’ Liberation movement. Essentially it’s “Mens’ Rights but not just fashy whataboutism”.

There are some legitimate complaints about how discourse on /r/MensLib can tend towards self-flagellative virtue signaling despite aiming to be a male-positive space. It is, on the whole, however, Cool and Good. Most people who complain about it are just incapable of understanding that the basis of male oppression is in the same toxic-masculine and patriarchal social norms that harm women.