I don’t think it ever ends and I don’t think it needs to. We live the human experience which is subjective and we use language to communicate that experience. Until we become a singular entity we will always rely on language to externalize our world, because of that we should always think about the language we use to communicate and express ideas. Words shape the world we see and the world we experience.

The point is, there will always be something some people will find offensive. How long before "animal" or "robot" are found to have undesired connotations?

Robot is an excellent example: it originates with the Czech word robota, which means forced labour or slavery.

We've been policing language through social norms since language was invented, so I'll bet on never.