Supporting an organization like the UFC that encourages people to beat, bloody and knock each other out for profit and entertainment is, though tempting, neither ethical nor Christian. Can you honestly imagine Jesus having a front-row seat to a UFC fight getting rowdy and encouraging a bearer of the imago dei to beat up another bearer of the imago dei? I cannot.
Christians with an inclination towards satisfying their violent urges in this manner would do well to read Augustine's recollection of the story of his student and friend, Alypius, recounted in book 6 of his famous Confessions. Christians are supposed to be in the world but not of the world. Do not degrade yourself with such folly. Remember who you are: a divine breath created out of the effulgence of the Supreme Mind, placed in a vale of soul-making in order to become the greatest possible type of created entity: a freely and unconditionally loving alter Christus.