To me, there is nothing wrong with the word 'master', as such.  I mastered Python to become a master of Python.  Purging Python of 'master' seems ill-conceived.  The word 'slave' is different matter to me.

In tk and tkinter, the 'parent' and 'master' of a widget may be different widgets, but I cannot remember the functional difference, nor whether the terms are used consistently.

Like Larry, I object to action based on hidden evidence.