On the one hand, this should just be switching a single variable. On the other hand, I'm a programmer and I should have learned by now that things that sounds simple rarely are, especially with old code.
I kind of like the idea of letting the player threaten Dean into being politer, but all it does is switch him to using the male dialog.
Something like "Call me babe again and I'll break your arms", and then he refers to you as "bro" from then on. Funny and relatively simple to implement.