The laws you are talking about are against discrimination, not against racism. The difference is discrimination is an actual concrete action that can be measured, racism isn't.
Abstract concepts such as "racism" aren't mathematical. There is no universal and unequivocal definition of what racism is. If we go simply by what the dictionary says, WhoreNickels' show wasn't racist:
And since you, and many others, did think her show was racist the only explanation is that there is more than one definition at play. Unlike concrete realities such as an apple, or a chair, where all of us would absolutely agree without a shadow of a doubt that something is or isn't an apple, you can't do the same thing with abstract concepts.
This is what I was trying to convey to you. That in the same way you think "using art as an excuse to allow racism" (or one definition of) is a "slippery and irresponsible slope", banning things that offend you is too. If you allow every definition of racism going around to dictate what should and should not be allowed you will end up banning romcoms.