What gives Bitcoin value aren't its technical merits but the fact that people believe in it.

Much of the belief in Bitcoin is that it has a bright future. Certainly the huge price spikes we've seen were not triggered by equally large spikes in usage - it's speculation on that future.

I quite agree that if people stop believing in Bitcoin, that will be bad. A fast way to bring that about will be to deliberately cripple the technology in order to force people onto something quite different (which probably won't be payment channel networks).

I'd argue that if we didn't force through a 20MB fork now, and we ran into major network difficulties a year from now and had no other technical solutions, that maybe we would get nearly universal agreement

I doubt it. The disagreement seems more philosophical than technical. If Bitcoin fell off a cliff then that'd just be taken as more evidence that block chains don't work and we should all use some network of payment hubs, or whatever the fashion of the day is. Or anyone who doesn't want to pay high fees is unimportant. See all the other justifications Gavin is working his way through on his blog.

That's why I conclude the opposite - if there is no fork, then people's confidence in Bitcoin will be seriously damaged. If it's impossible to do something as trivial as removing a temporary hack Satoshi put in place, then what about bigger challenges? If the community is really willing to drive itself off a cliff due to political deadlock, then why bother building things that use Bitcoin at all?