Exactly this, if you help one you gotta help all of them unless it's against the law for them do to so (banned parties).
Stop with the stupid policing of "hate speech", this will just lead to anything even remotely questionable getting deleted/flagged (see current youtube ad issues, where basically everything gets demonetized and you have to appeal that to maybe get it back)
> The issue gets thornier when it comes to working with groups on the fringes of the political spectrum.
NO it does not get thornier/worse or anything like that, just let the parties advertise like any other party would be able to. Voters will decide if they want that party to represent them - that's not up to media or other any entity.
Edit: formatting, clarification