You make a good point Medius. It would be very harmful even if it's just a few isolated diehards taking up arms against the government. It would be a bad thing, and one that could easily lead to the government further eroding other rights and liberties which aren't even gun related.
That said, the American public tends to disapprove of vigilantism against law enforcement, even if they agree with the vigilante's principles. I think they would end up blaming the resisters for engaging in violent conflicts with the cops.
It could be comparable to the NSA situation. People hate it, but they're not willing to put themselves on the line to do anything about it, and those who do go rogue to fight it are received with controversial mixed reception AT BEST. More often than not, it's worse though. Plenty of people who are livid about the NSA will stay say that they don't support what Snowden did because they don't think it's cool to leak classified security documents, even if you're doing it for a noble cause.
Anyway, that's the state of our public today. They'll get angry enough from time to time that they go elect someone from the other party than the incumbent, but other than that, they opt to live with policies they find reprehensible rather than revolt against the institutions.