My guess is: The problem for an American company banning the president would be they now need to establish same rules for everyone, thus banning most modern opportunists and even some loudmouth influencers. Politically, they'd need to ban most politicians, leading next to just outright banning all political speech. Twitter as a private entity is free to do so with their own platform. However, there's no way to avoid a slippery slope if the company's platform policies start getting entangled into politics. Since the company can never "win" this way or avoid suicide, they choose to do what they can as mandated to combat fake news while trying to stay neutral. You can be sure they have an army of legal specialists behind them on this approach.

Btw, calling out a bully and liar to be a bully and a liar, is not "hatred", when it can be so easily documented.