In psychology, maturity is the ability to respond to the environment in an appropriate manner. This response is generally learned rather than instinctive.
Sounds simple enough, right? Unfortunately, not everybody is as capable as they should be at this point in their lives. I’ve seen it happen around me in various forms and situations, but the general process is this. Two people get into an argument, usually about something stupid, most likely a misunderstanding. Instead of being able to separate the argument from the person and the entire relationship (friends or otherwise), the situation is blown out of proportion to such a scale that the relationship takes irreparable damage, if not destroying it completely. I realize this may sound kind of vague, so let me give you an example from a couple of years ago.
This happened to some people in my environment. A friend of mine posted a picture on Facebook, because of course she did. Someone close to her disagreed with the picture. Instead of calmly explaining why they took offense, they got into a heated screaming match, unfriended, and caused a rift between them and other people in their direct common circle. Over a Facebook picture. Are you f*cking kidding me?
Look, arguments and disagreements are normal in any relationship. That’s just the way life works. What’s important is how you react in such a situation, and the key to responding in an emotionally mature way is to have an appropriate, proportional response.
So what are reasons for breaking it off with somebody? It varies, but usually the most common reason for any kind of breakup, romantic or otherwise, is when something is structurally wrong. The bad outweighs the good. It’s either that or you come across a dealbreaker issue. An example for me would be if somebody goes out to intentionally hurt someone for whatever reason. To me, that’s never justified and shows an evil streak that I just don’t want to be around.
Anyway, everybody’s at a different level of emotional maturity I guess. In the end you have to decide for yourself how much bullsh*t you’re willing to put up with from somebody.