Do authors have to be politically correct in article-writing?
In the absence of a compelling reason to not use politically correct language, authors should make reasonable attempts to minimize offending readers. Given the information you provided, there does not seem to be any reason not to use master/slave. The words, and even the context, do not seem inherently offensive and have an established usage in many fields. I suggest including in your response letter a statement that you do not see the established use of master/slave to describe communication systems as being offensive, but if the editor requires a change, you will be happy to comply (assuming you are).
Do authors have to be politically correct in article-writing?
No, they can choose to use loaded words that might detract from the point of their article.
Alternatives used in computer science are master/worker (in one of the most influential CS papers of this century) and supervisor/worker.
This particular journal, and this particular reviewer for this journal, have every right to establish their own standards for language.
It's common for standards around language to change, by region, and over the course of time, for a variety of reasons.
Therefore, yes, you should expect to occasionally need to change your word choice based on a publisher's preferences. It doesn't sound like anyone is calling you a bad person, or penalizing you for this word choice. They are simply asking you to change it.
Adding a personal note on this particular terminology: I'm well aware that it's common in technical environments. But, given that my own recent ancestors were held in a condition of slavery in the not too distant past, I've always personally found it a jarring and unwelcome reminder of a painful period of history whenever I've encountered it. I can't speak for anyone else, but I have to admit I count it only as progress if it is finally being phased out.