Bigotry with the Low Speech spell

I have a bigotted NPC wizard that believes that his own race is superior to the other races of men. He doesn’t speak the same language as his enemies and uses the spell Low Speech to communicate with them.

I’ve hacked the spell to reinforce his belief that his enemies are lesser beings. This is the same spell that he uses to talk to dogs!

The other races don’t use magic a lot. But if they did I think that I would rule that the Low Speech does not work in reverse to give some credibility to the the wizard’s bigotry.

Legit rules drift?

Sounds like the wizard created his own spell. Totally kosher (and bigoted).