I know someone brought it up earlier, but Louis CK's bit (before people realized he actually was a shitty person) was that he was acting AS a shitty person. He was saying terrible things that people knew were terrible, but always presenting them as being in the wrong, and the comedy was from the absurdity of this person describing and rationalizing in front of the audience how wrong he was (the way people can laugh at the garbage Trump spouts because it feels unreal at some point). Sure his reveal as actually a shitty person sort of re-contextualizes a lot of that, but you can see what the intended effect was. HE was supposed to be the object of ridicule in his routine.
Dave doesn't show any sign or indication that he has the same intent behind his trans jokes. He's telling offensive jokes and he's not the target to be laughed at. He wants to make the same kind of absurdist jokes, but he's not meant to be the object of ridicule. He's not telling these jokes as a means of describing that he's the bad person in all this. He's trying to make the case that he's in the right to tell these, and people telling him to stop or the ones that are offended are in the wrong.
People are right in saying that you "can" joke about any subject in comedy, but it doesn't mean you can joke about it from every angle. It doesn't mean every joke is sacred or immune to criticism, and the bar to tell jokes about certain subjects should be (and is) insanely high when you're not a part of the group you're joking about and your jokes have a negative sting to them. The right person with the right background and the right connection with both their audience and the community could probably tell "trans" jokes and not catch flak for it when you know the intent behind it.
Dave isn't that person.