Sarah Silverman has officially mastered the "sorry, not sorry" apology. Last night on Watch What Happens Live, Silverman fielded an interesting question: "What is the most regrettable joke you've ever delivered?"Silverman has been called out on several offensive jokes in the past (including a wage equality video that trivialized trans issues ). But to address this viewer's question, she focused on an episode of The Sarah Silverman Program in which she wears blackface. She didn't say she regretted wearing blackface on TV, however, but that she regretted that a still from the episode was put up on Twitter "totally out of context."Silverman explained that she tweeted out the still "when Twitter was new and the people who followed me watched my show, and it was from that show." She went on to say, "It's totally racist out of context, and I regret that."