Sure, you could (in theory) be impeached, if we had a Congress that was little more than a cow turd.

Did someone in the government stop someone from speaking or protesting?

That would be a violation. Tweeting criticism? No, just no.

It must be Constitutional.

All we have to do is reinterpret "Congress" to mean "the President" and "abridge" to mean "criticize" and make "freedom of speech" an absolute so that a judge can get up during a trial to campaign for a candidate, a teacher can get up to criticize whoever they like, and a preacher can order his parishioners to vote "in God's name" for the candidate of his (or in some cases her) choice ... all while mandating that nobody can dare utter a word of criticism against them.

Trump's breaking protocol. He's not the first to do it; he's doing it with utter abandon. But most only respect tradition when it gets them something, usually control over others. If it's in their way, these days the attitude is that tradition is old-fashioned and should be tossed in the dustbin. We'll make our own traditions, even if we make them on Sunday and discard them on Monday, and we have venerable "traditions" now that date back only 2-3 years.

(Where I work we had a "tradition" last year that we were to keep, except that we were told about this tradition for the first time the day before it was to be upheld. "We're keeping the tradition" meant "we're doing something completely new." By not doing it for the first time we were "breaking the tradition.&quot