sure as shit would generate a substantial counter-claim. It would also encourage a competing definition of "fascism," illustrating the importance of stipulative and/or ostensive definitions. It may also serve as an illustration of the concept of argumentation as a method of arriving at truth.

What you're describing here would be more in line with a formal debate or philosophy course.

This is a high school. Argumentative essays are very simplistic in that setting. You make a claim, explain the argument/provide evidence or examples to your claim for a few paragraphs, and then summarize and conclude. It's basically just getting your toes wet for researching, depending on the topic.