How can a sexual act be unnatural? Some certainly are dangerous, some harmful (such as forcing oneself on another) but humans have desires. That's natural. Maybe one person's desires are not the same as the types of desires most people have, but that doesn't make them unnatural. I will say though that to abstain is likely difficult for most people, and probably causes high frustration. I don't think it's a good idea to choose celibacy as a form of sacrifice. I think that can set one up for a challenge that may be too great. When you consider the social pressures on a catholic priest, he probably would rather fail in his celibacy than fail and harm his reputation, so I think celibacy as a sacrifice can entice one to act out on his frustrations in private ways, and that concerns me. Of course the average person doesn't explain in detail thier sexual lives to other people, but it's understood that if you have a partner, you're most likely partaking in sex. A priest has a reputation to uphold, and I think that complicates it. Gay sex is perfectly harmless and infact praiseworthy if all members involved choose to be, just as the same could be said of sex between members of the opposite sex.