Upon What Basis of Morality is Calling Homosexuality Sin Immoral Considering Everything Supposedly Relative?

Translate:

Isn’t it strange that many leftists say it’s immoral to call homosexuality immoral considering all morality (“except the ok’ing of homosexuality”) is found in the Bible? So shouldn’t those leftists be saying instead that there is no morality at all, that all of the Bible is (supposedly) nonsense?