My intention was to point out that my comment probably enraged that person. Now, why where they enraged by it? I wasn't being inflammatory in tone, nor was I being antagonistic. So what would it be?

As far as I can tell, people are enraged when they see something they don't like to be pointed out, pointed out. An "uncomfortable truth" so to speak.

So being enraged and then commenting with "how pathetic" probably indicates that the person deep down understands that it's true.