That's wild. I've never heard of one being stuck that bad. They're only supposed to have around 15 lbs of torque. It sounds like they used super glue on yours. When I whacked mine, it did make a cracking sound, so I kind of suspect it had some kind of thread sealer.
I have tried to think of how to word this without sounding like an insulting peckerwood, but don't know how, so I'll just say make sure you're turning it the right way. I was under the center of the car when I removed mine, and I caught myself about to turn the plug the wrong way, because I was working from the back side of the plug, and so it was clockwise to loosen based on where I was in relation to the plug. It's an easy enough mistake to make. Just trying to help. Don't shoot me.
__________________________________________________ _____
2005 BMW 330Ci ZHP Jet Black/Black with aluminum cube
Bone stock at the moment