In an interview with Ellen DeGeneres, which aired on her talk show today, Knight says something changed inside him when he overheard an argument in October between Washington and Grey's Anatomy co-star Patrick Dempsey during which Washington used the slur.
"It's an awesome word, isn't it?" the actor told DeGeneres sarcastically. "I've never been called that to my face. So I think when that happened, something shifted, and it became bigger than myself."
Shortly after the on-set dustup, Knight confirmed he is gay - the kind of public announcement he says isn't his style, but he felt was necessary.
"I was under no delusions," he said. "My friends on the set knew. We talked about it. Publicly, it's not my thing to call up People magazine and be like, 'Hey, you want to know something about me?' I could've just let it slide and not said anything, but it became important. It became important to make the statement."
In the Golden Globe Awards press room on Monday night, after Grey's Anatomy won Best TV Drama, Washington dubiously fielded a question from a reporter about the incident and denied using the slur, which rekindled interest in what could have remained a dead issue.
"No, I did not call T.R. a faggot," he said. "Never happened, never happened."
But Knight told another story to Ellen DeGeneres.
The talk show host said, "And then the other night at the Golden Globes, I guess Isaiah Washington is starting up the whole thing up again which is kind of crazy..."
"Yeah, he denied that he said it (faggot)," Knight said, "and I don't know what to say about it. But it's pretty bad."
Washington's denial also infuriated Grey's Anatomy cast member Katherine Heigl, who reproached her co-star during an interview Monday.
"I'm going to be really honest right now, he needs to just not speak in public. Period," she said. "I'm sorry, that did not need to be said, I'm not okay with it."
In today's interview, T.R. Knight also thanked DeGeneres for her courage in coming out as a lesbian 10 years ago.