When I was screwing in my buffer tube I had the buffer retainer pin depressed all the way, and before I knew it I had screwed the buffer tube over it completely. Now the pin is pushing up on the threads and I can't turn the buffer tube to unscrew it. Is there a safe way for me to remove the tube, or is my only option to just force it off and ruin the threads?

The problem you're experiencing is that there's a flat channel along the base of the threads to provide and alignment notch for the latch plate. The buffer detent is up in that notch.

If you've got a small screwdriver or dental pick/probe, you can work it under the lip of the tube along that same notch, and depress the detent enough to back the tube off without damage. If you're unable to get anything in there to depress the detent, then you'll likely bugger the first few thread turns, which won't destroy the tube, just make it a little messy, and that cosmetic damage will be hidden inside the receiver ring.

Yep, figured out the same thing just now. Got it off without too much damage. I'd say great minds think alike, but I don't think I have any sort of bragging rights in this instance. Thanks for the help!

I did the same thing once.  If you backed it off and the detent isn't bent, you're fine.  Otherwise, a new one is only a few bucks.