It's also that they're primarily lower classes of men, who society considers disposable, or something to be ignored, so their activities don't garner the same attention, and because they tend to keep their activities out of the limelight for the most part. There is plenty of backlash when pride rolls around.
One of the reasons troonism generates such disgust is because of its highly visible and transgressive nature; they don't keep to the shadows and just pop up occasionally to make noise, like gay men, but constantly push themselves to the forefront in every situation. They invade spaces they were not meant to inhabit, they force everyone nearby to participate in their sexual gratification, and they never, ever shut up.
I think, though this may just be assumption, that people in general feel less sympathy for males selling sex.
Everyone knows that if women buy sex, it's because she wants something specific, rather than satisfying a desperate need.
So, males who sell sex, it is also overwhelmingly to men.
Men are more expected to sell their physical labor if nothing else presents itself, like heavy site work, dirty work in factories, most kinds of casual unskilled labor.
Thus, a common perception is if they are selling sex, they are either lazy or hedonistic because they are doing it mostly to buy drugs and they can't be particularly fussy or have much self-respect.
People don't seem to believe that men can be coerced or manipulated into it in the same way.
A woman selling sex is often perceived as either doing what she must to feed the kids without the support of a man.
A male selling sex is just a filthy little queer indulging in hedonistic acts and partying.
There is some perception of this about Troons too. Especially Troons who indulge in sex work, and historically perhaps if not the majority, a sizable minority of HSTS and perhaps totally brainwashed young gay men were Trooning specifically for sex work.
I get that Troons want to break this stereotype, but it's the wrong approach to try to place sex work on the same society level as other types of labor as a means to changing this stereotype.
It can be legalized and de stigmatized that way, but trying to make it an ordinary part of life is damaging.