I don't like to see a cry of racism raised to obscure a problem with performance or a personal conflict with a supervisor, or simple bad behaviour, or especially to disguise the black person's own racism.
Racism is a real thing and it can have truly bad effects. Its practice has been limited by law for an important reason. So we should not be quick to dismiss someone's claim that they are a victim of racism. BUT false claims of racism serve to weaken the legal protections that we have, and they also provide racists with ammunition, allowing them to suggest that ALL claims of racism are false.
So yes, it is bothersome when false claims are made. It's as if the person making the false claim is willing to sell every other black person's legal protections down the river, so long as they get away with whatever the issue is. And laugh about it... Laugh in the faces of all the well-intentioned people, no matter their colour, who tried to put those protections in place for him or her. "Ha ha, you patsy. I played you for sure!"
But make no mistake - the protections are necessary. I've seen many a workplace and streetscene incident that was racially motivated, even when the person committing the foul was actually unaware of how their convictions about race were affecting their judgment! It's out there, believe me. Which is why false claims are so outrageous.