I think this is only true if you believe that jokes are the nudge that bigots and extremists are waiting for before they let loose. I find this extremely difficult to believe.
I don't think that anybody who would harm a trans person for being trans thinks to themselves "Hmm, I'd better wait until somebody cracks a joke about them on Netflix". Especially given that the jokes they tell amongst themselves are likely far worse.
But if you do assume Dave has this power, then you also have to consider the fact that (though you could be forgiven for not realising if you've only listened to the outcry) he also argues powerfully in support of trans people during the show. Does this mean that people who were thinking about harming trans people will now be disuaded?
Your point about closeted trans kids is well taken though. Interestingly, in all the conversations I've had here so far, you're the first person to mention them. And yes, I can see very clearly how any kind of jokes about trans people might make their lives harder. Again, I don't think Dave's special will be the difference between a parent kicking their trans child out of their house or not, but yes, that's an especially vulnerable group of people.
Here, I guess we have to weigh how much responsibilty Dave has for the actions of parents and other kids. And I agree that he does have some when he's heard by millions of people. How much, well, I think everybody would have a different answer to that.