That bolt goes through a metal sleeve which is probably where it's stuck.
Go to a hardware store and buy a cheap socket-you're gonna be smacking the crap out of it. Hose it down with WD40 or similar stuff. And I mean hose it down-all possible angles and directions. Jack up the control arm under the spring, but only enough to release any tension on the joint, so you are only going to raise it ab. 1/8". Put the socket on the bolt head and with a hammer smack it a few times. You may want to hold the socket with a pair of vise grips as it will go flying. You want to send shock waves through the bolt to break it free.
And if you completely bugger it up the new bolt# is W500746-S439.