> If I go to an empty lot and I put up 50 Mike yard signs, what’s the difference between that and a bot that makes 50 Mike tweets?

Because you're viewing it as solely advertising, you're missing it.

If you go out and buy a newspaper, and direct them to publish only favourable articles about certain people, you begin to run into problems. Like laws that govern bias and fairness.

Because this isn't advertisement - this is where people, rightly or wrongly, are going to get their information.