You're right -- it was a caricature, and it wasn't entirely fair.

I think your view of compromise is accurate.
But I want to complicate it a little. It may be true that there's a carefully balanced compromise, making everyone unhappy by the same amount, such that making a change really would make the system fall apart, with possibly disastrous results. The first thing I want to say is that someone who sees this "balance" may make a sort of mental shorthand and call it a good solution or a solved problem, and lose the acute awareness of grievance from the various unhappy parties. The moderate may eventually cease to recognize the grievances as even slightly legitimate. (I have seen this happen.) And this is a genuine fallacy.

The second thing I want to say is that the state of slavery in the 1850's was also a delicately balanced compromise, and disturbing it did have disastrous results. I'm not saying this to discredit your argument with a smear. My point is this: it may add zero new information to know that some people are unhappy with the status quo, but it does add information to know what their reasoning is for being unhappy. The content of abolitionist propaganda, the strength of its arguments as compared to those of pro-slavery propaganda, would sway a Martian observer trying to decide what he thought about slavery. If the Martian had only been allowed to see election numbers, poll results, legislative deliberations, and so on, he might have had a different opinion than if he had also been shown a few issues of The Liberator. In other words: the structure of a compromise is not enough to know whether you support it or not.