He's no good guy, but he's definitely not a villain. Captain Sprinkletits only does what he does simply because he hates his name. Yes, it's as simple as that.

Oh, I guess I sort of lied, he hates his mother for having given it to him in the first place. Now it's as simple as that.

Everything pirate that he's done is just to grind her gears. To Twilight's chagrin, she'd made it onto that short list.