Yeah, can't just look at locking the spare to the support. Have to look at the whole system and figure out how to immobilize each junction without making it a PITA for you to work on it. In my case that pivot bolt is torqued to 150 lbs-ft with red Lock-tite and then safety wired. That just made stealing the spare a whole lot more complicated in terms of the tools needed. You aren't going to stop them if they really want it, but you can make it too slow or painful to be worth the trouble.
When there is a accessible nut on such a bolt I've been known to drill the nut thru two opposing flats, torque it into place, then drill the bolt thru those holes, and drive a roll pin into the hole. If I want to be particularly evil, and I don't expect to need to work on it myself, I'll drive a second, smaller roll pin thru the center of the larger one. It's all about slowing them down, not stopping them.