Do you mean cut the head off the base? No problem!
Do you mean cut the entire thing down to the rock? Probably!
I've heard many stories about people having their toadstool ripped up or knocked off, and it grew back. The harder part is getting the frags to stick to the new plug/rock. I don't think I'd do it on purpose though. A bit risky in my mind, but you should have plenty of frags to replace it with if it doesn't grow back.