I read your post and the article. I caught the attempt at nuance in both, and, if the harassment is physical in nature or if it's verbal and the words cause or result in physical harm to whom they are directed, then they may or may not be protected speech under the First Amendment.
However, if the words are just words, and the words do not result in physical harm to whom they are directed, then they are protected. Some physical acts are seen as speech, even if there are no words used. As an example, the burning a US flag by protesters who are protesting a group of US veterans could very reasonably be described and defined by the veterans and others as harassment of the veterans by the protesters, yet it's still protected speech because no actual harm was created or resulted from the act. There are thousands of other examples.
Verbal harassment, and even some physical acts of harassment, that don't cause or result in physical harm, is ... protected speech.
Edit: For you and anyone else that is actually interested in the facts, here's a rather left leaning group's opinion:
https://www.aclu.org/other/freedom-expression