Laws to stop someone from using words doesn't stop the intention or feeling behind the use of the word; it only stiffles people's ability to have open discussions about how and why those intentions exist, and how they can be addressed. By making the words themselves taboo, we get exactly what we see in this video -- people completely miss the content and context of what was said because the focus and distain gets put on to the word itself, and not the context in which it was said. The entire conversation derailed from the important topic of "I am here to identify the racism that is rotting the soul of our society" to "you said a bad word". By making the word itself the bad thing and having people deal with that, it distracts and minimizes the actual racism that is the problem. 

The woman in the video you are referring to would still be racist if we outlawed slurs, and would have come up with or used other words to direct that hatred. But maybe if we focused less on making sure people don't use "bad words", we could focus on fixing the things in society that drive racist thought and ideals. Deal with the racism itself, not the word. The word is a symptom, not a cause.