It's probably OK to do some tapping with a plastic or rubber mallet, just don't go crazy on it with a ball peen hammer. You don't want to break / detach / demagnetize the magnets in that rotor cup.
I think I got a tool for pulling it off of ebay / dennis kirk. It was cheap. If I recall correctly, it's just more or less a high grade bolt with proper thread (which I think is a big size, but a standard thread).
+1 on the alarming noise... I popped one off a KLR-250, and thought I broke the crank based on the minor explosion that went off when I finally got it to let go...