I would just like to point out that the movie never said Ares was responsible for everything; in fact he himself outright said that all he did was give a bunch of people who already wanted to cause massive amounts of destruction ideas on how exactly to go about it. Ludendorff would still have been a pure evil monster even if Ares hadn’t given him and his assistant some ideas for how to kill people more efficiently.

I mean, I won’t deny that the Ares reveal does cheapen the movie’s overall impact somewhat, but I don’t think it’s quite as bad as you say it is. That said, this does at least sound interesting.