I think I can safely proclaim my theory here:
The D stands for Dick. Monkey Dick Luffy, Portgas Dick Ace, etc.
1. Blackbeard is a total dick. No denying that one.
2. Garp greets his grandson by socking him in the face. Dickery abound? I say yes.
3. Sauro picked up boats and threw them around instead of just smashing them. I can safely say that overkill is dickery in a situation like this.
4. Luffy tried to eat Chopper once, didn't he? Dick.
I can come up with theories, too.
Just saying things doesn't really make them anymore believable. So Davy Jones revolutionized the world with his games? Fascinating. What does that have to do with Luffy.
Don't you have anything better to do at 6:42 AM than flame people for no reason? If you don't agree, fine. But don't be a preschooler.