Let’s get this out of the way first: it doesn’t matter that he said it in the heat of the moment. It doesn’t matter that the particular word he said is used much more liberally within baseball clubhouses than it is in many other environments. And it doesn’t matter that he said it to a fan who was being an ass.
All of those things are true. But none of those things change the fundamental fact that the sole purpose of that word is to denigrate and intimidate an entire class of human beings. No one uses that word unless they believe that an entire class of human beings deserves to be denigrated and intimidated because they are who they are, and unless they want to denigrate and intimidate an entire class of human beings because they are who they are.