That's assuming you want to quit the job. But given the employer, the opportunity to learn a ton if I stayed and my low self-esteem at the time I wasn't overly eager to quit.

Doesn't this run afoul of the 'don't badmouth previous employers' rule?

It's expected that you aren't going to be gumdrops and rainbows about your prior employer in an interview. The point of this rule is that you don't look like you're bitter or holding a grudge; if the new company thinks you create vendettas whenever there's a problem, they're going to want to stay away from you for fear that you'll be unfair to them if such a misunderstanding arises in the course of your employment with them (e.g., hurting their reputation in the marketplace, leaking source code because you're mad at your boss).

It'd be reasonable to say something like "We had different perspectives on the structure of the workplace and it just wasn't really what I was looking for". They'll probably ask "Oh, what was the issue?" and you'll say "I needed to work remotely to be at the bedside of an ailing parent and they said they'd fire me if I tried, so I quit".

You don't want to look like you're blaming them for making you miss your parents' final moments (we're grownups and take personal responsibility for things like that, don't allow people to stop you from participating in important life milestones), which is why it's a good idea to allow them to dig a little bit before getting at the real dispute. This is a good principle when discussing previous employers anyway. You always want to sound like you're over whatever the slight was, that you see and understand their perspective and don't blame them for having it, but simply don't agree with it. You won't be faulted for that.

That's a good rule of thumb for a variety of reasons, but this is a situation where I don't think it applies. (1) It's the truth, and it's the reason you're seeking a job, and any worthwhile employer would likely sympathize. (2) You've already burnt your bridge with the previous employer, so who cares?