Maybe things look different today but those are some pretty good reasons for why it is the way it is today.
Most of the homophobic is used it's used to describe a situation where somebody isn't actually afraid of gay people.
I think it actually is a legitimate argument though that the feels of the entire gay population is more important than the reals of the very small amount of HIV infections that would realistically happen just because one number is so much larger than the other and HIV is far less consequential than it was when this policy was enacted. People tend to be bias towards avoiding extreme outcomes over causing a much lesser outcome far more often. See: nuclear being perceived as more dangerous than fossil fuels.
In any case there’s so many more important issues out there than blood donation among men who have sex with men the entire dispute smacks of bikeshedding. People are both discriminated against far worse, and are killed far more often, by different issues. It matters very little if people have the wrong opinion on this issue relative to if they have the wrong opinion on different issues.