Again, you never allow players to persuade an NPC to do something they would never do, so, why are you allowing an NPC to do it? If the NPC tries to persuade the character to do something the character would never do, it's treated exactly the same way as the player trying to do that to an NPC.
Where is the problem?
To me, it's far more about portraying an actual, believable character. We accept the dice telling us all sorts of things about the character, so, I have no real problems with this either. And, there are many ways of doing it. FATE's Aspects is a great way, for example. If your character has a particular Aspect, the DM can target that Aspect and the player can then behave as the Aspect demands, or pay the price to change the Aspect. In either case, the character's consistency is maintained.
In D&D terms, if your character has a particular Flaw, the DM could target that Flaw and you would either have to play out that Flaw or pay some sort of price to resist the Flaw. In any case, the character is still maintained.
For some bizarre reason you seem to think that if the DM has the ability to influence your character, the DM is going to ruin your character. Given all the flack I take over not trusting DM's, this seems to be the most damning condemnation of DM's. Allowing an NPC to convince the PC to do something through a skill roll is somehow going to "ruin" the character? What happened to "trust your DM"?