There's not a doubt in my mind that if Mr. Rogers had known about trans kids, he would have invited them onto his show, shown them love, and taught a lesson to all of his viewers about pronouns.
@JessTheUnstill Considering he had a gay cast member that he supported his whole life, I fully agree. If the show had gone on longer they probably would have even addressed it (I'm not surprised they didn't in the 90s or earlier ofc).