breaking promises and being a jerk

[Duck-Of-Doom]

Hi.

This won't be covered (I am assuming) by official rules, but I was curious to as what most people think about breaking promises in munchkin and/or being a jerk in general.

For example, someone might not have something to bargain with in regards helping/not helping out in battles. Once in a while, we have exchanges like, "If you let me beat this monster, I promise I won't be a jerk (ie. curse, attack) to you".

And then the very next turn, you might attack that person when they are trying to beat a mosnter, or curse them with something really mean, in essence, breaking your promise to be nice to them.

Is this frowned upon, or is it fair game?

Viewpoint 1) It's a promise, don't be a jerk.
Viewpoint 2) It's munchkinly and there was nothing official so anything goes.

Thoughts?