I've never seen the desirability of protecting children from facts about the world. We want them to learn that one and one equals two, why then conceal from them that some people are trans? It's useful information. Some of them may be trans too and will be glad of the role model. Besides, the sooner they learn about such things- and how ordinary they are- the less chance there is of them growing up to be bigots.
But, then again, if there were no bigots in the world there'd be nobody for Richard Littlejohn to talk to- and that would be sad.