I don't think you have to directly attack idealism or religion per se. I mean, for people who have even a casual interest in history, in 2020 I feel like a lot of people recognize the flaws in viewing history just as great men conducting wars. There's a huge interest in understanding how people throughout history just lived their lives, as well as understanding what "really" happened and what were the true driving forces of historical events. I think you just have to start there.

And for people who don't care about history, whatever they're not going to be interested anyway.