I'll admit I'm confused with the two concepts of standing firm or walking away in the face of a major shit test.

Last week my now ex starts calling me some stupid nickname on the phone to which I reply I don't like her calling me that way. she gets really upset gaslighting me how I'm too sensitive and no fun at all. Since I our relationship was already fucked up at that point I eventually ended up apologizing for ruining her mood (broke frame for the 50th time). In hindsight I should have staid with my point that I just think it's disrespectful. Easier said than done.

Until what point do you stay with your point and when do you just leave the room / end the call? Just for the future.