As I understand the situation, Ellen is lesbian, and understandably is not inclined to provide a platform for a homophobe to preach her agenda of hate.I'd take this to be relevant to topic.
http://ew.com/tv/2017/01/03/ellen-degeneres-kim-burrell-cancelled-tweet/
Yes, it's Ellen's show, Ellen has the right to refuse guests, who likely are paid a premium to appear. Ellen, however, isn't willing to allow a performance by a person of a different understanding or frame of mind. Burrell isn't "trolling", these are her genuine convictions. Yet her talent and conviction just doesn't gel with Ellen's identity agenda and thus she is not welcome, she is censored from appearing in Ellen's "space".
That, regardless of how understandable I see Ellen's decision, is the practice of "safe space". She wants to be seen as equal, supposedly, but does not feel others belong in "that" equal. It's rational, it's "fair", but something seems deeply disingenuous about the plight, continuing forward.
I don't see a problem with her decision.