Likeness proceeds along various spectra. No two ideologies are "the same" if you pick the right spectrum on which they differ, and many are the same if you pick spectra on which they are the same.

Communism and fascism are alike in that they deny that they may be wrong. In a democracy, politicians recognize, if only by accepting the results of elections, that they may be wrong, that if the voters want something else, the voters should have something else. That's why Trumpism is "like" fascism: it argues that the voters cannot possibly prefer something else, which is just another way of saying that they will not be permitted to prefer something else.

The important thing about communism and fascism is that they are equally to be feared. Everything else is a detail not worth considering.