It seemed like he got mad because when she pisses on him, he mumbles something and she apologetically tries to wipe the piss off him but he's clearly not having it.

Also you'll notice the next time Ms. Rivera has to piss on Ange, when she's riding Max reverse cowgirl, he has her a little further away to prevent himself from getting pissed on.

One thing I really wish Max changed is the formula he uses. His first scene seems to be where he concentrates all his budget and resources with the last 2 scenes always feeling like throwaways.