Thanks for your replies so far everyone.
Now that you mention it, I probably did come off as a bit too forceful too soon. In my defense, my first message (in the quote section of the "demands" PM, bottom half) after having discovered the problems was relatively polite and reasonable; the "demands" PM was sent after he failed to reply for almost a week. The "threatening RCMP report" came a month and bit after that "demands" PM in the hopes that he would at least reply. And I debated with myself for a while about how threatening and impolite my messages should be before sending them, and after having received no reply to my first PM for about a week, I figured the seller felt he hadn't done anything wrong and was therefore not obligated to reply. But you're right; I probably should have been more polite and my explanation doesn't really excuse my rudeness. If this ever happens again I will definitely be more reasonable.
Then again, DarkAngel, I'm sure you'd never omit massive amounts of significant information about something you're selling (intentionally or not) and then fail to reply when your buyer has problems with it.
in reply to AngelusNex:
Some may consider the negative feedback I received to be arguably justified; I don't want to colour your perception of this dispute with my language. As DarkAngel pointed out, I was a little rude in my PMs. I only feel the feedback he gave me was retaliatory because he posted it right after he found out I gave him negative feedback and because he didn't reply to any of my PMs, rude or not.
Just so you guys don't have to form your own interpretations based on my description of the problems, I'll take pics soon and edit them into the first post.
Again, thanks for your replies guys