There was a time the lab leak covid theory was hate speech, people were calling people racists for mentioning it. Sometimes simply stating statistics can get construed as hate speech.
I'm sure there's other good examples, but at the end of the day it just creates a bar for those trying to silence a topic to reach.
Holocaust denial is not hate speech. People should be allowed to question a historic event. People should be allowed to think.
I think you got the facts mixed up. The person who wrote the op ed was not an American citizen and they were not jailed, they were ordered to return to their home country. They were on a student visa which is conditional and it is a privilege, not a right. They raised some flags and the student visa was revoked.