What if it IS what my character would do?

[Rater202]

Nope. Why is it always "kill anyone who does x or die trying"? Who in real life does that, for anything? Opposing x wherever you encounter it is a good and flavourful character trait, and there are multiple ways to oppose something that is both non-disruptive, and in fact could even create content for everyone at the table, but just ratcheting it up to "must engage in violence immediately, to the death" is just massively inflexible and unrealistic. Apply some nuance to the trait and everyone benefits, play it flat and uncompromising, and that's when you have a problem.

You're missing the point.

the point is that in this scenario, "kill slavers whenever we encounter them" has been a permitted behavior for the entire campaign so far.

It is only when the PCs are enslaved by a corrupt Government after being framed by a crime that killing the slavers—in this case,t eh people actively trying to enslave the PC—becomes disruptive.

That's not the player's fault. He is playing his character the exact same way he's been playing that character for the entire game. He is being consistent.

If it disrupts the game now, it's not his fault, it's the fault of the GM for changing the rules without talking to that player first and working with him to find a way to do the plot he wants without requiring to player to play his character in a way that goes against everything established so far in the campaign.