Because when it actually comes down to it, they don't give a damn about "social justice", equality or making things better overall for the people they deem to be oppressed. All they care about is having their voices heard and valued- and everyone else silenced. There's an inherit power that comes along with being a victim in today's society, as we allow these people to turn around and say "everyone who isn't me must shut up and listen, as your opinions aren't valid". Instead of working for actual change, these pseudo activists work to place themselves above those they see as opressors.  It's human nature to want to feel special and  like your voice and opinions matter, more so than others. The victim narrative allows people to do this. All this does is create even more fustration and resentment in those that they try to silence, which in turn creates even more hatred and prejudice against the original "victims" (victims in quotes as I do not see fat people as an oppressed group. Other groups obviously have legit grievances). On it goes, back and forth, and nothing ever changes and no constructive dialogue ever takes place. Which is the true intention of the media which has bred and fostered this toxic culture- to keep people divided and distracted by bullshit social issues.