If an old friend does things you dislike (Part1)

Everyone has his own likes and dislikes. When you are socializing with others, there is a moment when you find out that a friend does something you don't like/something that annoys you (loathe = far too strong). At this point, you might wonder whether you want to continue to be friends with that person. (whether you continue interacting with the friend or not is already a thought in your mind = things would be easier if you tried to stick to Subject-Verb-Object or Subject-Linking Verb/Copular Verb- Complement sentence structures. Your sentence structures are often very complex, and you are setting yourself up for mistakes). If an old friend does something I am not comfortable with, I would continue our friendship.

I believe that when friends do something I don't like, they must have their reasons/they are doing it for a reason. (Here again, you chose a very complicated way of saying this.) Friends should trust each other. That reminds me of something that happened once ("event" is used for something more important). First let me explain: I dislike being stood up ("in the last minute" is redundant: if someone stands you up, it always happens in the last minute: you can't stand someone up in advance, because standing up means not to show up). Once one of my old friends and I decided to see a movie, but ten minutes after the movie had started, he still hadn't shown/showed up. (This sentence was really unclear, in part because you got the tense wrong.) I went into the cinema anyway. Above all, I was annoyed that he hadn't called me to tell me that he couldn't come. (Primarily = too formal, I was pissed off = rather vulgar; by his absence without giving me a call before the show started = not idiomatic). After that, he sent me a message to explain/explaining (as a non-native speaker, it is usually better to use the infinitive construction rather than the participle, because it is much easier to make mistakes with the pariciple).  his unintentional absence. The reason he did not show up (on time? he didn't show up at all, I thought) is that he had lost his phone and right after getting ready ("all set" usually used in declarative sentences such as "I am all set.",) a professor told him to come to the lab as soon as possible (he was informed by the professor to go to the lab as soon as possible = no reason to use passive voice here; is it really one specific professor? Otherwise use "a")) ,which he did not mean to. (Not clear what you mean here.) So I was not angry with him, because he didn't have any other choice. (Do you see how it is possible to say everything you want to say using the same comparatively simple structures? So it was an accident,which at last I found it acceptable after being aware of the inevitable cause. = not really clear.) An old friend can give an explanation for doing things I find unacceptable. If it is due to a plausible reason (awkward, but okay grammatically), I will not give up our friendship. (I would say, "If he has/gives me a plausible explanation for what happened, then ....)

Even if an old friend is behaving badly, there is always the chance that he can change. (Notwithstanding = more complex word that you don't need to use at this level;  an old does not have the rightness = abstract word - not used with article here; ,I still find it possible for him to alter = usually used transitively i.e. with an object). If a friend has the intention to get things right (a bit vague), I ought to be clear that there's no need to leave a friend because of an isolated case (incident = better), (which will show more neutral in this = unclear).One thing that I really hate is when someone swears all (of) the time. (Here again: you use a structure that is needlessly complex - and wrong: One of the things I hate when people do is swearing all the time.)An old friend of mine, (no comma here) who used to talk in an uneducated way: he constantly used bad words and wasn't even aware that he was doing that. Then I compiled a list of the disadvantages of swearing for him and steadily and respectively (respectfully?) discussed it with him. (if you illustrate something, you describe an imagined scene: "Let's suppose you are meeting your girlfriend's parents and you suddenly said a bad word unconsciously"). Soon he came to understand the downside of speaking bad words, which are a sign of  rudeness, a bad upbringing,  and disrespect towards the people you are talking to. In the end, he broke himself of this habit and no longer talked as rudely as he had before. When an old friend does something I dislike, I will lose a friend if I stop hanging out with him because of it. It is unkind/disloyal if I don't give him a second chance (impersonal = a fairly neutral word.) If he still does not change anything after a second chance, it gives me sufficient reason to stop seeing him.