Lance Bass is making an impassioned plea to the FDA to end its longstanding restrictions on gay men donating blood ... saying his blood is no different from that of straight donors.

Lance told us it's a travesty gay men can't donate if they've had sex within 12 months -- especially after tragedies like the Las Vegas massacre. He added ... there's clearly a need, and the only possible reason to stick with the policy is to discriminate against the gay community.

He said so with much fewer words though. Two letters to be exact.

Lance says if America won't come to its senses on gun control, maybe it can at least remove the stigma about gay blood. He's not mincing words either, and directly calls out the American Red Cross.

Another singer, Jeffree Star, was at LAX when he echoed Lance's feelings, telling us, saving lives should outweigh bigotry. 

HOW IS THAT OKAY!?
TMZ.com