A less generous interpretation is that they coordinate harassment campaigns against transgender people and have caused at least three suicides.
One of the three suicides seems to have not happened at all (would have been reported to the US consul in Japan), two others were attributed to posts that did not comply to KF moderation standards, were created by freshly registered users and were removed much faster than similar stuff typically remains visible on Twitter of Facebook.
Thought experiment: if KF founder committed suicide, would you demand deplatforming MotherJones?