The holes themselves are never tapped. Usually there is a nut that is held from turning by a metal strap clipped to it. That strap lets go and lets the nut spin. First look if there's an access hole where you can get in with Vise Grip pliers to hold the nut. The next thing is to use a wire-feed welder to tack that strap back onto the nut. The strap breaks off because the nut is rusted to the bolt, and very often the heat from welding the strap back on helps break them apart.
If there is no access hole, you may be able to cut one with a torch.
Another alternative is to use a Sawzall with a metal-cutting blade to cut the bolt between the cross member and lower control arm. That will allow you to get the control arm out of the way, then you can use an air hammer to move the nut. From there you have the option of installing a new bolt and nut, but those should come from the dealer to be sure they're hardened properly for the application. Use anti-seize compound on the smooth part of the bolt where it goes through the sleeve in the bushing so that doesn't rust tight next time. If you're reusing the control arm, you may need to use a hydraulic press to remove the bolt if it's rusted tight.
Two words of caution about that bolt. First, don't get any anti-seize compound on the threads because the nut will never stay tight. Second, the car's suspension must be at normal ride height when you tighten control arm bolts. Too many people tighten those bolts while the car is jacked up and the suspension is hanging down. That clamps the bushings in a permanent twist and will greatly shorten their life.
Monday, June 15th, 2015 AT 6:26 PM