Right, but in that case the problem isn’t posting one-sided content, or content that favors one person over another, but posting poorly sourced content.
I find it dangerous to say “we’ll ban people who mainly post about one person” because the US presidential race, for better or worse, is about two people. Expressing any opinion at all advocates one of those people above the other. Put the rules in terms of quality of sources, though, and you will find that you can solve the same problem without the same baggage.
This is a News forum, it seems reasonable to vet sources.