It looks like the crack is on the metal casing where the throttle normally flicks back to and is stopped - looks like the tag has pressed back too far and caused the crack.
What is the "tag" you're describing, Dale? I can't picture it or the damaging action you're describing either. It might be time for bed. From here, that looks like a crack that might occur when an BMW assembly like that one was dropped or was forced onto a 7/8" handlebar.
Anyway, if that is a 22mm bar and it were my bike, I'd syringe some JB Weld or its equivalent into that crack after gently spreading it slightly, clamp if for a few days, cover the crack with paint, reinstall it and forget about it.
