All caught lying to the blood bank as revealed by tests should be prosecuted for attempted murder.
Private Organizations may specify any Contractual Requirements for association that they wish. Those who deliberately and knowingly attempt to perpetrate Fraud upon such private organizations, are at the very least guilty of an act of Criminal Mischief of ethical similarity to Tresspass or Vandalism -- and should be prosecuted accordingly.
If the Red Cross wanted to develop better information, I guess they could ask if somebody has had unprotected homosexual sex within since 1973 and then follow up with HIV testing questions and ask if they have done so within the last six months. However, from their point of view, it is more practical to just exclude the entire population, and take blood from a lower risk group. The increase in the number of available donors that would result from a more thorough screening is so small that the added complexity and possibility for tragic error is not justified.
It's a practical issue, not a civil rights one. Nobody is denied a civil right because they are unable to give blood. In fact, one can donate and have a completely confidential way to opt out from having their blood transfused, if one is under societal pressure to donate.