A letter from Germany, page-17

A polemic is a controversial argument. The letter looks like a statement of facts to me.

If you disagreed with the factualness of it, you might have an argument

polemic synonyms: diatribe, invective, denunciation, denouncement, rant, tirade, broadside, attack, harangue, verbal onslaught.

None of those fit the bill either.

Unless we are going to live in a society where, upon looking out the window on a sunny day and remarking that the sky is very blue, one is called a polemicist. How that is going to help us, I'm at a total loss to understand.