I use BLUE loctite on collapsible stock lock rings and a tad on the tube. Never had a problem. It is recommended. Sure, it doesn't come right off, but it ISN't SUPPOSED TO. No damage. Don't use RED. Consider red a permanent thing, and I agree, anyone using red for this application is a wank. I use blue on my ARMS 40, my LMT BUIS, some scope mounts (NOT torx ring screws), etc. If you want to constantly swap stocks, tubes, etc., then don't use blue loctite. If you intend to shoot your AR and use it, a little blue loctite is highly advisable, and a good thing. By the way, if you don't agree with me, you better drop a line to Tango Down (and every other grip manuf.) and warn them. They have the stuff pre-applied to their grip screws. BTW, those grip screws are steel, and they thread into aluminum. However, remember that with blue, also BUY THE PROPER WRENCHES AND TOOLS. Otherwise, removal will be a metal marring, frustrating experience.
Edit: As ShadowOne said, moderate use of blue loctite. If you use too much, it can be a real b!tch. A drop or two at most.