True, but their proofs had to be read. Their papers and books had to be read in order to be tested. Furthermore, those books and letters and papers contained content that was not purely mathematical. Especially in Newton’s case. Hell, iirc he disses on other mathematicians frequently in some of his works. But did that make everyone who read them hateful? Did people reading his works negatively impact the world? Would it have positively impacted the world if everyone had decided not to read any of newtons work? Or Schrödinger’s?

No. Of course not.

Now I’ll admit math was a poor choice for comparison to Harry Potter, but the point remains that bad people can make/discover/influence good things. And consuming media related to a bad person is not guaranteed to have a negative impact on your wellbeing.