They are sometimes referred to as 'The Brides of Christ' but it's not a primarily sexual context, more the idea of fidelity and loyalty. They take an oath to essentially be 'joined' to a life of religion the same way two people take an oath to be joined when married; marriage isn't all about sex, nor is a woman taking holy orders.
I think the Prof's distinction between abstinence and celibacy is valid. Abstinence, to me, suggests it's a temporary thing. To a catholic, Lent it a period of abstinence. To a muslim, Ramadan is a period of abstinence. These are for a set period of time and most people who undertake them probably would consider them a 'spiritual learning experience'. Abstinence forces us to examine why we desire that thing we are abstaining from and therefore know ourselves better.
Celibacy is a different thing, IMO. It is not an act with an end point. It doesn't 'run out'. Celibacy is a statement that you are leaving those aspects of yourself behind as a sacrifice because doing so gives you a different perspective, a vision no longer tilted by the instinct and desire for sex. Whether that's actually what happens or not I couldn't possibly say but my catholic upbringing suggests that's what it's supposed to represent anyway.
To me, it doesn't really matter if a religious figure notionally was hetero or homosexual. Once they take a vow of celibacy they are saying 'my sexuality is put aside to allow me to follow a different path', so at that point it becomes irrelevant. It's interesting that some religions require celibacy and some don't; To be honest I've never really seen celibacy as a requirement for someone to be wise and give good advice but if that's what some religions require I have no real authority to say they are wrong. However I have always considered that the one area an avoutly celibate organisation has absolutely no right to lecture anyone else about is sex...
Jon