Ok, explain this to me

So, I'm driving on I-16 yesterday, heading back to Savannah. It's early and there's not much traffic. I set my cruise control to right around 70 mph.

I gradually creep up behind this guy driving a Horizon who is apparently driving 69 1/2 mph. When I'm close enough I shift over to the left lane to pass. As I start to go around the other car--still without touching my gas pedal because the cruise control is on--dumbass speeds up.

So, I slow down, shift back into the right lane. What does dumbass do? Right. He slows down again. So, I get back over to pass and he does the same thing.

I up my speed to 75. Dumbass likewise speeds up but driving that fast scares him--he just can't bring himself to go any faster than that, and he loses his nerve after a quarter mile or so and I go around him, finally.

I leave the cruise control at 75 and continue crusing along, and what happens next but dumbass blows past me, changes lanes until he's in front of me again, and then slows down until he's back inside his comfort zone. We begin this stupid game again.

Now, I don't give two sh!ts if I get passed. I usually don't even notice. Just don't pass me, get in front of me, and slow the f#ck down.

This seems to happen to me a lot. Cars will be creeping along, oblivious to other cars blowing right by them. Until it's me--then they seem to feel like I'm posing a threat to their manhood and if I successfully pass them, their penis will withdraw into their bodies and they'll be forced to wear skirts and have sex with men for the rest of their lives--though this isn't always men. Once it was a little old lady.

Are you one of those people? If so, could you explain to me what the hell you're doing? I'd love to know.