In a certain perspective, by quitting this conversation you too „don’t care“ about what latchkey thinks about this topic, though „someone somewhere“ (most likely their employer) definitely cares that they would tolerate the behavior your coworker displayed. You are doing what they propose, just at another perimeter of tolerance.

I don’t think that you „fundamentally disagree“, but that you have different understandings on when the time has come to quit caring. And given the limited amount of things we can care about during our lifetime I find it certainly helpful to reevaluate from time to time what I decide to care about.

I agree that your coworkers behavior is harmful to a team’s productivity and I would seek the conversation to resolve the disagreement in a professional manner. But if there is no path of a resolution, I would escalate the problem, stop caring and get on with my life, because there is nothing more I could’ve done.