The benefit of someone writing vapid, extremist nonsense on blogs is that I believe he already declared his violent intentions, repeatedly, in public, in a medium that is preserved at dozens to hundreds of locations even if he changes or deletes the originals

. I imagine his writings are why the Feds got an arrest warrant in the first place, and I'm sure his writing will be Exhibit A for the prosecution. I expect he's going to aim to be a martyr for the cause like the Times Square bomber guy, though, so it's not like the Feds will have to work very hard to get a conviction. It does definitely throw cold water on the theory that he was some kind of anti-Muslim sock puppet, unless you want to fall back on the usual conspiracy theory nonsense about "that's how deep the conspiracy goes, man!"
That being said, I don't know that this arrest makes it more likely that the banned episode will air now. It's true that the immediate threat (such as it was) is gone, but the fact that he was about to leave to go join a known terrorist organization could just as easily be used to justify the censoring and its continuation. This guy was not just some fool posturing for the Internet, he was apparently the real deal: an honest-to-goodness, "I wanna kill infidels" extremist. If Comedy Central were going to explain itself (and they haven't so far, so I don't see why they'd start now), I'd expect them to fall back on a "dodged a bullet" defense and say they did the right thing by acting defensively in the first place.
I still think that's totally bogus and that the episode itself is winning the battle to lose the war, but I wouldn't expect the status quo to change just 'cuz the Feds made an arrest.