They are being told which gender they cannot marry. That is gender discrimination.
No different than being told what race you have to marry.
Your argument is as stupid as when interracial marriages were illegal and some bigoted idiot (redundant phrase) like you would say, "No race is being told they can't marry."
What's stupid is your knee jerk dumbing down understanding of Loving V Virginia. The decision wasn't based on people not being able to marry another race,
it was based on the law being applied unequally, utilizing racial discrimination:
"There is patently no legitimate overriding purpose independent of invidious racial discrimination which justifies this classification. The fact that Virginia prohibits only interracial marriages involving white persons demonstrates that the racial classifications must stand on their own justification, as measures designed to maintain White Supremacy".
This is why it doesn't compare to marriage laws that don't discriminate and are applied equally to all people. Now you know.
Or not.