I was baffled at first by this comment, but then I realized it's the recent tend in the USA to somehow make up for the mistakes of the past, hence the attempts

I was baffled at first by this comment, but then I realized it's the recent tend in the USA to somehow make up for the mistakes of the past, hence the attempts to erase words like "master/slave" that are perceived as sad reminders of unfortunately not-so-distant past. In Europe, we don't see this way as we don't have this particular trauma. We did have different forms of slavery centuries ago, but it was newer a thing in mainland Europe (although the feudal system was close to it). So this word is not that emotionally marked for us. It's quite normal to say that someone is a slave to something (fashion, fear, alcohol). Some people even use it in a positive way, e.g. a slave to God. All these figurative uses are quite common and are not intended to trivialize the original meaning.