Most Helpful Guy
I wouldn't be cool with it, and I'm sure not really many people would be.
I'd talk to your boyfriend about it and try to say to him how it makes you feel, even when he's taken, trying to kiss him while his girlfriend is like right there is disrespectful as anything.
Most Helpful Girl
No you shouldn't be. I wouldn't let any random girl kiss my man even if it was a cheek kiss