Executives at TV network ABC are have slammed Grey's Anatomy star Isaiah Washington's use of a gay slur at the Golden Globe Awards as “unacceptable.” Washington stunned cast mates in the press room at the awards show on Monday, when he insisted he never used the word “f****t” to describe gay co-star TR Knight during an on-set spat last year. ABC issued a statement Thursday saying, “We have a long-standing policy to create and maintain respectful workplaces for all our employees. We dealt with the original situation in October, and thought the issue resolved. Therefore, we are greatly dismayed that Mr. Washington chose to use such inappropriate language at the Golden Globes, that he himself deemed ‘unfortunate’ in his previous public apology. We take this situation very seriously, and his actions are unacceptable and are being addressed.” Knight told talk show host Ellen DeGeneres Tuesday that he had, in fact, referred to him as a “f****t” during a scuffle with co-star Patrick Dempsey on the set last year. Fans of the medical drama are also on the attack - in an internet petition, which was sent to ABC bosses Wednesday - over 8,000 viewers asked TV executives to fire Washington.