I can't speak to the agenda of r/MensRights, or whether or not this is a case of feminism gone too far, but it must be said that your post is itself pushing an agenda to discredit comments posted here by implying that critical comments are Reddit plants linked to vitriolic posts you found there. After all, your Twitter feed states that you're a feminist and criticizes "gender role enforcement" on Hacker News, which suggests you're coming at this story from a predisposition. That's fine, but it means your warning may be tinted by previously held views.
To my knowledge, nobody is putting forth the worldview that men are being terrorized by women destroying lives. However, there are people who believe that losing a job over something so far removed from anything that actually matters as an overheard dick joke is step in the wrong direction for gender equality, especially when Adria made the same kind of joke herself.
As for calling her a liar, that stems from the discrepancy in accounts. The guy who was fired claimed there was no sexual innuendo in the forking comment, and that it was applied by Adria in her telling of the incident.