If you can't formulate an argument as to why "master" is meaningfully better than "main", you are no better than the culture warriors who insisted on changing it in the first place.
How/why to justify something that was unjustified in the first place?
I'm not asking you to justify something that was unjustified in the first place -- I'm asking you to justify what you're asking people to do now. Why is it worth everyone's time and effort to migrate back to using "master" rather than "main"?
To remove the political prejudice injected into it.