If somebody is being obnoxious and trying to show off by dropping words of another language into their speech, I think it is better to laugh at them (quitely) rather than get angry. I used get really annoyed at how obnoxious people were, but really there's no point in being angry. After all, most people will see how silly this somebody is, they are causing themselves enough damage as it is. Laughing is all you can do! (and hope it is a phase people grow out of)
But what's most impressive is that there are people who manage to sound ridiculous and obnoxious in only one language! No need to rely upon misused French to sound silly, for an example just read anything by Germaine Greer, or anything by literary theory academics!
Painting: Chop Suey by Edward Hopper