Freedom of speech applies to everyone, not just the speech one doesn't like. While foreign nationals may not have the right to vote, like it or not, they do have the same right to stand on a street corner and espouse their viewpoints.

It has also been decided that purchasing ads is covered by the same freedom.

Sadly, what the people that want to shut down other people offering their opinions are really saying that US citizens are too stupid to make their own decisions. They are attempting this censorship under the guise of protecting simpletons from being influenced to vote a certain way.

It's a very slippery slope to try and draw a line between freedom of speech and influencing others.  After all, isn't that what freedom of speech is for?? Whether it is to buy a BMW or vote for Donald Trump, it is still a protected right to be able to publicly state one's opinion.