The idea is that changing language can help to change the debate. And, of course, it has a long history and does work: nowadays the use of the "n-word" on TV is uncommon and always considered offensive; the introduction of the term "gay". There are many examples.
For myself, I find it hard to get excited about "master/slave", simply because in the UK at least it's largely historical. Perhaps, that is a luxury others do not have. One of the things that I do find amusing, though, is all the people who like to spend their time commenting on what a waste of time this is, when we should be coding. And others complaining about the principle of trying to change language to change the debate, and then blaming it all on SJWs and snowflakes: terms invented in an attempt to change the debate.