I feel like a majority of shippers don't treat their slash ships as canon. Sure there's a vocal and toxic minority, but those fringe voices will always exist within any subculture. That's just how subcultures work. Imo this feels like an overstatement of harm which draws attention away from legitimate criticism of slash fanfic (e.g. racism and flanderization)

Laying the lack of platonic male friendships at the feet of slash shippers also feels both misguided and scapegoat-ey. The more obvious culprit imo is the media industry which spends billions of dollars to often diminish and pathologize any representation of emotionally intimate and healthy male friendships, rather than Becky next door whose online capital comprises the 60 followers she has on AO3.

Not to mention, many slash communities often attempt to grapple with toxic masculinity in ways in which mainstream media often refuses to. This is due to how the impulse of fanfic often comes from the desire to respond to perceived absences, shortcomings, or missed opportunities in the source material (albeit clumsily at times). Consequently there is a wealth of more healthy depictions of male friendships to be found in slash fics (outside of the slash pairing). Sure that representation isn't always perfect, but at least there is more often than not an attempt. And this coming from a gay man who finds myself alienated from slash somewhat often, and has a bevy of my own criticism.

Also bi/pan/closeted gay people exist. And it should go w/o saying that babies aren't exclusive to straight men.