Regarding Colbert, in Malcolm's words: is he too stupid or too full of himself to notice that what he does is morally indefensible?

Althouse has referenced Janet Malcolm's book "The Journalist and the Murderer" before.

It seems that a corollary to her thesis is The Talk Show Host and the Guest.

From Wiki:

"Malcolm's thesis, and the most widely quoted passage from The Journalist and the Murderer, is its opening paragraph: "Every journalist who is not too stupid or too full of himself to notice what is going on knows that what he does is morally indefensible." 

Replace 'journalist' with 'talk show host' and you get a steroidal example of this truth.

Further, the talk show host can simulate this relationship without even speaking to the 'guest': it is in the monologues and quips, where a straw-man phantom of the guest exists, to be used as a piñata by the host.

Regarding Colbert, in Malcolm's words: is he too stupid or too full of himself to notice that what he does is morally indefensible?

Yes, yes: embrace the power of 'and'.

But I believe Colbert is smart. His ego has made a pact with the devil, and the morally indefensible is easily side-stepped by self-congratulation and a sense of righteousness.

I suspect his audience will eventually turn on him; after all that's what mobs do.