It's how they liberate themselves from their oppressors. They genuinely believe that looking attractive, looking like a normal man or a woman, etc are evil and tools of the patriarchy/whatever to oppress them. It used to be goth, or grunge, or any number of other rebellious fads that have waxed and waned over the decades going against society at large. The difference here is their rebellion is being back up by institutions like the MSM, colleges, etc and has achieved a near religious level of reverence. Old or traditional = bad. New or different = good.