You're at a friend's place when you meet someone.
The someone is annoying as hell.
You're polite because your friend does business with them.
You run into the annoying person a few days later and they are even MORE annoying and...slightly offensive.
How do you react knowing you met them through someone they do business with who is a friend of yours?
Does respect for your friend cause you to be as polite as possible or, since you're somewhere else and the friend isn't around, are you comfortable tagging that azz?