I don't quite disagree with this, but I'm willing to defend those who do because a slightly different weighting in my priorities would make my disagree.

Inciting violence should be punished by the law, not by Facebook. For regular people it makes sense to outsource some of this to Facebook, to minimize the load on the legal system. POTUS however is one very high profile person. His statements are not being missed by those who have the authority to enforce the law. There is public debate ongoing over what should be done. Facebook should not need to help out here.

Of course, as a result of an ubstroctionist attorney general (the baseless memo protecting the president from prosecution) and Senate (refusing to convict for political reasons) Facebook might actually be the best practical route, but them having to take that roll is actively damaging to society.