They're just following their own rules.
ESPN sent out the following memo to their affiliates today:
Effective immediately, Ultimate Fighting Championship (UFC) ads are no longer accepted on the Disney & ESPN family of networks. UFC ads are a direct violation of our Affiliate agreements "Affiliate shall not insert into the ESPN network advertisements or promotions of any sports program." Please contact your programming colleagues for complete advertising restrictions. ESPN is not accepting these ads on a national level, and the same restrictions apply for our local Affiliates. Thank you for your cooperation and immediate attention to this matter.
“I Just Killed Kenny! You Bastard!”