This is a Danish stamp (by Torben Skov) from 1990 promoting a campaign against bike theft. It says roughly "Take a bike - Your own!" or "Ride a bike - Your own!"
Stealing or damaging other peoples property can have consequences and just apologizing might not help. I was going to post a video here about street justice, which many of you have seen already, but it has been removed from YouTube. For more info see CWMD.