Long story short, some retard at work left a bit of their paint on the rear door of my truck about a month ago. No metal damage, no visible scratches or anything, just red paint... How do I get this off of my paint without doing further damage?

 

I would try claying it first and see what happens. Just make sure you use lots of lube while doing this so you dont do more damage.

 

Yeah, least agressive first.

Try clay (I've tried it several time and have not personaly ever seen a clay take paint transefer off)
if not then move up stepwise to more and more abrasive pads/polishes till it comes out.
Of course there is a point where you have to stop and consult a pro or body shop but it doesn't sound like your going to get to that point.
I have had good luck with ScratchX, Megs #9, Megs #80, & Megs #83

 

If clay doesn't do it, give it a quick swipe with lacquer thinner. Follow it up immediately with some wax.