Watch Stephen Colbert massacre Dinesh D'Souza by choking him with cream here (part two, youtube link).
Some background: Dinesh D'Souza is one of those American "conservatives" who believes that Osama bin Laden hates liberal, secular Americans who allow gay rights, and is the author of a book expounding the thesis that the liberal left caused 9/11. The book has largely met with the contempt it deserves, but D'Souza has managed to get op-ed space in the LA times and elsewhere to expound his thesis.
Meanwhile, Stephen Colbert is a "fake interviewer" who (like Sacha Baron Cohen) achieved much notoriety in 2006. Both were already well known, Cohen for "Da Ali G Show" and Colbert for his previous role in "The Daily Show with Jon Stewart"; but Cohen's movie "Borat" and Colbert's TV show "The Colbert Report" (which debuted in late 2005) brought them to new audiences, as did Colbert's infamous live roasting of Bush at the White House Correspondents' Dinner -- something few, if anyone, have done to Bush's face, before or since.
Unlike Cohen, Colbert wears no disguises and does not change his name for his alter ego -- he only changes the pronunciation of his surname. His chosen "role" is an aggressively right-wing TV host in the mould of Bill O'Reilly (not the cricketer). Thus, where a typical liberal may try to argue with Dinesh D'Souza, Colbert merely pretends to be O'Reilly or Sean Hannity and eggs him on, but exaggerates the material to such a ridiculous level that even D'Souza is left squirming and attempting to deny the premise of his own book.
Most of Ali G's and Borat's hilarious interviews were made when the guest had no idea who the interviewer was: "Borat" was made in America partly because Cohen and his characters were less well known there than in the UK, and with his new celebrity it is unlikely that we will see a "Borat II" (Cohen is planning a new movie on his third alter ego, "Bruno", but it remains to be seen how that works out). Colbert, too, has suffered a shortage of right-wing targets lately (with left-wingers such as Neil Young, his role tends to descend into buffoonery, since he's not actually disagreeing with them -- though it's fun to watch all the same). But he still seems capable of occasionally ambushing the likes of D'Souza.