Jesse Jackson has a very personal reason which fueled his widely circulated remark that he wants to "cut Obama's nuts off" for "speaking down" to blacks. What Jackson calls talking down to blacks is Obama's telling black churchgoers, as Bill Cosby has told black groups before, that they must stop blaming slavery alone for their communities' troubles: "Too many fathers are AWOL, missing from too many lives and too many homes. They've abandoned their responsibilities. They're acting like boys instead of men," Obama said.
The reason Jackson took this constructive criticism so personally is that he's one of the "boys" that Obama is talking about. Let's not forget that only a few years ago Jackson was discovered to have fathered an illegitimate child, and because of his other, "legitimate" life he couldn't be around for that child as often as one might like him.
In fact, if someone had cut Jackson's nuts off in time, he wouldn't be so angry at Obama.