You're not going to just rip/pry the mirror off the mounting button/base. You will need a small flat head screwdriver. Insert the screwdriver into the little slot opening on the bottom of the mirror mounting bracket till it's jammed between the tab and the mounting bracket, and gently tap at it with the rubber mallet. It shouldn't take much force at all with the rubber mallet if you've placed the head of the screwdriver where it needs to be. I'm pretty sure there's a special tool out there for them, but other than that, there's really no other way to remove the modern mirrors than the technique described. I wish they would have just stuck to the old torx screws.
