I don’t think it’s an oxymoron, because the question, “Can heterosexuals be celibate?” is also a valid question.
There are plenty of heterosexuals who have made the personal decision to remain celibate for a higher personal goal.
The desire, in the abstract, to engage in sexual relations with a person of the opposite sex is not a desire to commit sin. It becomes sinful when the desire is specifically directed toward someone other than one's spouse.
The desire, in the abstract, to engage in genital arousal conduct with a person of the same sex is inherently a desire to commit sin.
Thus the normal person who abstains from sexual relations is giving up one good for what he perceives as a greater good.
The person who abstains from homosexual genital arousal is abstaining from that which is inherently evil.