Because you know exactly what people mean when they talk about fascism. Trumps fascist language and tendencies have also been well documented by scores of people and not just progressives. Instead of deflecting by debating about the meaning of the word, explain how you're ok with all of the fascists things that he says on a regular basis.

As someone else said who responded to you, they could list all the fascist statements Trump has made and you'll find reasons to dismiss them. Just like trying to convince a religious person that god does not exist.