Its my understanding that body dysmorphia is best treated with anti-depressants in most patients. Anti-depressants have no effect on gender dysphoria. If anti depressants aren't working, maybe some other kind of intervention is warranted for those patients.
I do not understand why being against it is transphobia, but I would like to understand this better.
FFS is a reconstructive surgery. It is hard to compare to anything, but the purpose is to revert disfiguration by having the improper hormones. If cis people had this issue with hormones, then of course they should be covered.
I'm not sure about it either, I just know that it seems to be the most clinically significant treatment. Most people with body dysmorphia regret their surgeries, rates for trans regret are extremely low. Usually in the range of .5%-2% depending on surgery. For reference, somewhere around 30-40% regret knee surgery depending on the study. Regret rate science is a pretty well established thing.