The Bible does indeed explicitly forbid homosexuality as a cardinal sin.
Leviticus 18:22 Thou shalt not lie with mankind, as with womankind; it is abomination.
18:23 therewith; neither shall any woman stand before a beast, to lie down thereto; it is perversion.
24 Defile not ye yourselves in any of these things; for in all these the nations are defiled, which I cast out from before you.
25 And the land was defiled, therefore I did visit the iniquity thereof upon it, and the land vomited out her inhabitants.
26 Ye therefore shall keep My statutes and Mine ordinances, and shall not do any of these abominations; neither the home-born, nor the stranger that sojourneth among you—
27 for all these abominations have the men of the land done, that were before you, and the land is defiled—
28 that the land vomit not you out also, when ye defile it, as it vomited out the nation that was before you.
29 For whosoever shall do any of these abominations, even the souls that do them shall be cut off from among their people.
30 Therefore shall ye keep My charge, that ye do not any of these abominable customs, which were done before you, and that ye defile not yourselves therein: I am the LORD your God. {P}
Bible - Leviticus -
You want to leave out the rest of the chapter? The entire 18th chapter is dedicated to sexual sin, and homosexuality is not mentioned as “especially”. Sexual sin is “especially”. This is emphasized again by Paul in 1 Corinthians 6:12-20.
I pursued this issue extensively after being challenged by a friend when I stated, incorrectly, that homosexual sin was a worse sin than the heterosexual sin of which I was guilty.