Oh, thanks for the references.
I'm constantly astonished at how people can think "filter bad words" would fix everything. In some instances of Tay tweets, there are comparisons between black men and monkeys. What words should you forbid? Black, man, or monkey? Should the bot be allowed to speak about people of color visiting a zoo?
This is supposed to be AI. I'd expect it to know what words and phrases mean, and how sentences are structured. I'd expect it to know that some people are black, and people can visit zoos, and zoos often contain monkeys. I'd also expect it to know that comparing people to other animals is potentially offensive, and to avoid saying those things just to be on the safe side.
You certainly can't make it perfect, but in this case, where the submitter is effectively anonymous and they're not paying for the service, you should be able to justify the occasional false positive.
It wouldn't result in a very smart or fun AI. Tay was supposed to be fun because of its intelligence. Throwing a braindead solution intended for dumb forum software would run counter to the project's goals in my opinion.