The way to "defeat" Christopher Hitchens in a "debate" is to employ lots and lots of rhetoric aimed at an impressionable crowd. Hitchens can't speak the language, and ends up looking less intelligent than Galloway, though I dare say the opposite is the case, by far.
The typing here is not meant to be absolute, but I believe it to be correct.
http://youtube.com/watch?v=INy2ysHhgYM
http://youtube.com/watch?v=zH_BULU2vcM