This new ban doesn't attempt to isolate risky behavior of donors, it just bans certain people categorically regardless of the facts of their life. For instance, a single straight college student vs. a gay man who has been in a monogamous relationship for the past five years? Who is at greater risk for exposure to STDs or HIV?
The one thing I haven't seen anyone openly acknowledge-- now or a few years ago when these regulations were first considered-- is this ban really about a fear of having gay children?
The average hetero couple that goes to a sperm bank is often trying to match the characteristics of the donor to those of the future father-- ethnicity, eye color, height, interests, etc. And since we really don't know what makes a person gay, what if by choosing a gay donor a couple will always wonder about little Johnny or Mary? I think that HIV may be a bit of a red herring, that the FDA would like to reassure people that they're not trying to make a possibly gay baby with a gay man.