You can call another player a piece of s**t on the field. You can call his mother a whore. You can insult his country. You can come up with the most vile, disgusting stuff imaginable - and nobody bats an eye.
But say something racist and people call for you to be banned from the sport.
The double-standard is just a product of identity politics. All of the above are awful things to say/do. One isn't substantially worse than the others. All of them are a reflection of poor character.