I recall hearing that LBJ once called someone a "200-proof, double-dip motherf----r". Can't find the link (it was way pre-internet).
LBJ was famed for his colorful speech (and you must admit, that’s not only colorful, but pretty funny!) but he usually kept it to conversations with private parties and it wasn’t meant for general consumption. Occasionally he’d do something just to shock (such as showing off his appendectomy scar to the press) but in general he behaved himself in public. The same is true of Nixon, whose speech wasn’t colorful but just nasty, and Clinton, who was given to bursts of anger and whose speech was crude and full of expletives...but not for the news media or the public.
The difference with Obama is that he really has so much contempt for us that he doesn’t care, and he has systematically been cheapening the office of President in every way, from his media call-ins (remember the “Pimp with the Limp”?) and appearances with foul-mouthed, grunting rap “artists” to his own personal speech and behavior in public.
That said, I think with Obama and Biden both these are attempts to portray themselves as something they’re not, by adopting behavior they think would typify the image they want to express. Obama is very effeminate, and he probably thinks a “real man” would speak crudely and bluster. Biden is a product of a private school education and a family that, except for a couple of years, had money and thus he has absolutely none of the “working class” background that he has tried to adopt as a condescending, insulting vote-getting mechanism. But in his tiny mind, he thinks that a working class man would make “manly” remarks such as the appallingly crude comment made to Woods’ father, and that this is reinforcing the image of Regular Joe.
In any case, no matter why they do it, they’re disgusting.