Social media sites really need to face the decision of whether they're "common carriers" or are liable for consequences of discrimination against common/normal views.
when an ad causes serious consternation in the press, they pull it because "we've a private site and can regulate speech".
But if there isn't sufficient controversy, they can hide behind the banner of free speech.
Sites like Facebook need to either commit to allowing all lawful ads, or admit they exercise editorial judgement on what is "proper" speech, and start a larger conversation about what sort of speech should be restricted.