Language is the road map of a culture. It tells you where its people come from and where they are going.
— Rita Mae Brown
On the one hand, it’s my opinion that the specific word someone uses means very little compared to what they mean by that word.
On the other hand, yes, vocabulary changes over time. “Decimate” used to mean “kill one person in ten”; nowadays it means “destroy most of”, almost the opposite of its archaic meaning.
But context matters. Intent matters. Chasing the term-of-the-moment is a distraction from what actually helps or hurts people. This semiotic scavenger hunt is one of the ways in which well-meaning people are kept occupied by trivia, while the Republican death cult burns the United States to the ground.
That being said, if someone from Mexico tells me that they consider “Mexican” to be pejorative because someone, somewhere has used that word as an insult, I will make an effort not to use that word around them. (Note: this is a hypothetical example, but it very easily could be a real-life example tomorrow.)