I dislike developers who make needless refractions such as changing the names of methods or moving parts of the code to different files all because then they understand it beter in that case.

Is that developer right to also dislike you for wanting master? Where does that lead? Conventions aren't based on feelings, and you should have none towards them. Everything has a reason, and reasons can be compared and weighed. Main is shorter, for one,, I like that, and also newer, master being the legacy convention. What are your arguments?

When you try to write a story and they turn every story into at least 2 stories, applied recursively.

... yet he has not handed back his Master's degree.

It's one thing to have (childish, misguided) principles, another thing entirely to inflict them on other people before looking at oneself.