No, this is not FUD. This is a proxy for a pattern of behavior (unprotected sex with the same sex, sharing of needles, etc). They ask you these questions as a primary filter for determining who is at risk of transferring a disease. We still don't know everything about how the disease is transferred, but we know which behavior patterns lead to it.
And regarding the 1978 date, we still don't even know how long HIV can lay dormant in humans.
Your grand-grandparent post quite emphatically is FUD. Being MSM is positively correlated with a pattern of behaviour that elevates risk of HIV. So is being a college student. So is serial monogamy. So is being a heterosexual male. Singling out one of these while making no attempt to break down the diverse group MSM by further detailing high-risk behaviour and black-marking it with an ominous question like "Do you really want the donation pool potentially contaminated by the HIV virus?" (who does?) is very much FUD against MSM as a whole.
I'm sorry if reality offends anyone's PC sensibilities, but in the US MSM account for 49% of HIV cases[1] despite accounting for a small percentage of the population. MSM are MUCH more likely to get HIV than, say, frat boys who casually hook up with a lot of females. I'm not sure if the ban is completely justified, but there is potential reason behind it.
The statistics do not offend my sensibilities. The FUD does.
There is a long way between "up to one in five MSMs are HIV-positive" to dismissing discussion on whether all MSMs should be banned from donations for life with "Do you really want the donation pool potentially contaminated by the HIV virus?"
49% of HIV cases are MSM, not 49% of MSMs have HIV, don't twist it around. You are trying to make it sound much worse than it really is, when in fact it's a non-issue, thus spreading FUD. Very few MSMs have HIV.
49% of HIV cases = 580,000 cases. That's a staggeringly high infection rate in the MSM community in the United States - more than one in ten. The CDC estimates that one in five gay men have HIV in a study of 21 major cities, and that 40% of them don't know it.
And regarding the 1978 date, we still don't even know how long HIV can lay dormant in humans.