(And by "ignore," I mean I'm going to say just this: Daily Show-co-creator Lizz Winstead says (to Alyssa Rosenberg at ThinkProgress) that one of the difficulties of conservative humor is that it's harder to defend the status quo with humor. That doesn't seem right to me; I agree more with Martha Nussbaum when she pointed out that parody can be used for progressive ends (parodying gender norms) or for conservative ends (parodying the flaunting of gender norms). Not all subversive parodies are progressive.
(I might want to say that, even though it's easy to imagine conservative humor existing, there isn't a lot of it around now; but the truth is, it's probably just not very funny to me. Like pictures of Obama as an African witch doctor--that shit probably kills in certain circles.)
Now that I've ignored that bigger question, let's get to the particular question: is Colbert good for liberals?
Some friends and family recently told me that they feel bad for Colbert's liberal guests, since the guests can't keep up with him; and since Colbert is such a magnetic personality, the audience might end up liking him and his conservative/ironic worldview. In other words: the sincere liberals look like saps and the "conservative" ironist looks affable and calm. (Unless Jane Fonda is crawling into his lap. More of this, please!)
Satire and parody are notoriously difficult to read; and Colbert is a great example of that, since he was the object of that study that showed that liberals see him as satirical and conservatives see him as sincere. And part of that problem is that today's conservatives seem largely to exist in a realm of self-parody--it's not always easy to tell The Onion from The New York Times when the subject is conservatives.
But however much fun Colbert is to watch, I think his character remains distant from the audience for several reasons, not limited to his stupidity and venality. (His shilling for Prescott Pharmaceuticals is in the same register as his shilling for Republican policies.) Even more important, Colbert remains distant precisely because of his irony, which is not too hard to recognize most of the time.
(And if you don’t believe that, you could watch his regular show and his show from Iraq and notice the difference; Colbert breaks character sometimes to laugh at the jokes in his regular show, but he breaks character all the time in Iraq when he’s talking about something he sincerely cares about.)
So, yes, Colbert sometimes steam-rolls his guests, and if he’s talking to liberal guests, it can seem as if his steam-rolling is bad for liberalism. But I don’t think that’s the case, because in those situations, the joke is usually on Colbert; for instance, when Colbert asks a guest, “Bush: great president or the greatest president?,” we don’t laugh at the guest, who can’t answer, but at Colbert, who has such a limited view of the world and is clearly cheating to maintain that worldview.
So I don’t think he’s bad for American liberalism. We like watching Colbert, but no one wants to be him. Unless Jane Fonda is crawling into his lap.