Why not? I know it sounds horrible, but unless the ads explicitly serve child porn, a platform for legalizing child porn is merely a political position and covered under the first amendment.
You can go to a city hall, and start making your case for legalizing child porn and they can't do anything to prevent you from doing that (legally).
I know you're using this example as a rhetoric, but in US simulated child porn (like anime) is already legal and protected under the first amendment.
> Embeds to 'make the US a purely Christian nation' groups, if they call themselves 'allow "traditional" values in the court room' groups?
Either you don't live in America (or recently moved here) or you live in a deep bubble. I have seen ads about making America a Christian nation, similarly ads about putting traditional values in the courtrooms (check out the whole ten commandments in courtroom controversy).