Betrayal of Trust...

Wikipedia says:
Betrayal
-as a form of deception or dismissal of prior presumptions, is the breaking or violation of a presumptive social contract (trust, or confidence) that produces moral and psychological conflict within a relationship amongst individuals, between organizations or between individuals and organizations. Often betrayal is the act of supporting a rival group, or it is a complete break from previously decided upon or presumed norms by one party from the others.

When you have tremendous respect for someone and they do something to break your trust... that is the ultimate Loss.

Perhaps my trust was simply misplaced. Perhaps you never deserved that trust. Perhaps you misrepresented yourself from the very beginning or maybe I saw what I wanted to see. But I am not alone. Several of your friends believed better of you and now feel the loss. I know all the people you work with believe you're "made of gold". Can it be that the pressure of living up to THAT is causing you to let the rest of us down?

Now, you've allowed one of us to be seen in a bad light... you've allowed it because YOU know the truth and have not spoken up.

Here's my suggestion... you can say, "It was meant to be a joke." "I didn't mean for it to get out of hand" "I didn't want anyone else blamed"
How's that? Pretty simple isn't it? Please, do the right thing!