I'm not sure but I think you're saying that (ignoring the uncertainty stuff) the Republicans weren't doing anything at all wrong right up until the moment of the shutdown, and only after that were they behaving inappropriately.
Correct (ignoring uncertainty stuff, though, which I don't think you can do, but we'll set this an alternate universe where the US had fixed terms on debt or something).
I remember lots of denunciations of political hostage-taking before this happened though. And it came up with the Bush tax cuts expiring and during various budget fights. I understand the game theory behind why a party would engage in hostage-taking, but it seems to me to be a thing that we should disapprove of if we want a well-functioning government. And mostly we do disapprove of it. There's a reason parties are rarely explicit that their strategy is to force a game of chicken, and it is generally not that they hope that decision-makers on the other side will think that they really don't care about the thing they're playing chicken with.
I think these are two slightly different arguments. I mean, generally speaking, I think people do what they have the most incentive to do. If your problem is that people have an incentive to play chicken, just hoping they don't play chicken probably isn't going to be effective. Instead, you need to change the incentive structure. For example, I heavily oppose the idea of a federal debt ceiling. I think it is a ridiculous idea.
The problem is not really down to the Republicans themselves that American government doesn't do well - I mean, they're the mechanism by which it doesn't function well, but they're a product of their political environment. If I were a Republican, and I mean a genuinely principled one, who cared about the concerns of my constituents and wanted to represent those concerns, I would also play chicken in this scenario (not to the point of shut-down, which is stupid, but certainly as long as I could until that point). I would not be doing them justice if I failed to do this. The problem comes from before the fact that Republicans do this (except when it causes a shut-down, which again, to stress, is incredibly harmful), and start with the mechanisms that are in place that make this the best thing to do.
And, like, if hostage-taking is a legitimate strategy then surely it is also a legitimate strategy to say "you're hostage-taking and that's a shitty thing to do". I mean, how do you expect actors to respond to these kinds of strategies if not by drumming up indignation on their side about the other side using the strategy? These disputes get resolved when someone blinks and so it seems totally reasonable to create a lot of "we don't negotiate with terrorists" -type sentiment so that the hostage-taker has no reason to keep the hostage because he believes you won't blink.
I don't think it's illegitimate to say "that's a shitty thing to do". I think it's just pointless. I mean, with most of these things you know in advance what's going to happen, it's just that everyone has to go through the motions because that's what makes it happen. That's why I've been saying multiple times we may as well just nap until the convention. The next few weeks is going to be Sanders savaging the DNC, Clinton supporters savaging Sanders, ad infinitum. Very tedious, and we could talk about more interesting things.
And the point of chicken is that both sides want it, so it's pretty difficult to say one side is hostage taking more than the other. One could say Clinton's refusal to compromise more on <X issue> is the hostage-taking. It's only because you have a normative notion before entering this that Sanders ought not receive <X issue> that you perceive him as the hostage-taker.