Those which are non-falsifiable do not contradict objective reality - by definition. We can show someone the D&D rulebooks, and show that there are no instructions for actually enacting magic of any kind within their covers - that claim is falsifiable. I cannot prove that some supernatural power didn't assist in Aunt Martha's dramatic and unexpected cancer remission.
Aren't objective reality, so we have no issues there.
None whatsoever. That's the point - within some very broad cultural norms, you can believe what you want in those regards, without comment.
It is okay to ridicule someone ascribing ascribes a moral flaw to people out of ignorance. The books are easily available. The speaker could look and see that there's nothing real there, but has failed to do so.
We live on a planet with several billion other people. If you go about calling things evil, without learning directly about them first, the results are on you.
As if we could measure it?
Ridicule, like any tool, can be used constructively or destructively. In this case, given that the person in question will never know of it, it is not likely to be either. Expressing opinions about it here is ineffectual and harmless.