Not what I'm saying, and I know you don't understand the problem, because you're talking about spell save DCs which are not skill checks and are specifically under DM purview as a magical mind altering effect.

Think of it like this:

You have the right, as a player, to decide your character fucking hates someone so much they will not believe a word they say under any circumstance.

That would be, in terms of interpreting that to mechanics, setting the Skill DC to "impossible." Which is ALWAYS AN OPTION FOR SKILL CHECKS. You can not jump to heaven with an Athletics check (normally speaking).

It could be you're metagaming, but that's a separate problem beyond the scope of skill, ability, and spell save checks.