Well, it's uncertain if he was a misogynist or not, but a lot of historical texts make that claim, so Hima-sensei reading them for his research would likely come to that conclusion. Google search for: Frederick the Great misogynist, and you'll see a lot of results that make the claim.

He certainly didn't want a female ruler for whatever reason, and other than a marriage forced by his father (which he ended as soon as the father was gone), he didn't associate with women much at all. Though it's also theorized he was asexual or homosexual. Whether due to derision toward women or just preference to men, who knows.

I won't take it as fact since it's not known for sure, but with so many historical sources going so far as to claim he was a very open misogynist, I can't blame Hima-sensei for coming to that conclusion. The guy was still an awesome ruler regardless, especially with an awful start in life.