You would have to ask those people to answer that themselves. There's no question that homosexual acts are forbidden by the Bible, but so are many others acts that these same Christians seem to be able to live with. Why they are so afraid of this one sin so much more than any of the others is something I can't explain.
Leviticus 20:13 for instance certainly pulls no punches:
If a man also lie with mankind,
as he lieth with a woman,
both of them have committed an abomination
.
But the same chapter also forbids incest and consorting with wizards
or people with familiar spirits
.
It also condemns anyone
that curseth his father or his mother
,
and these Israelite civil laws go on to say:
And the man that committeth adultery with [another] man's wife,
… the adulterer and the adulteress shall surely be put to death.
In the New Testament, Paul writes
neither fornicators, nor idolaters,
nor adulterers, nor effeminate,
nor abusers of themselves with mankind,
Nor thieves, nor covetous, nor drunkards, nor revilers,
nor extortioners, shall inherit the kingdom of God.
In other versions, effeminate
is translated as
homosexuals
or sexual perverts
.
So yes, the Bible does condemn homosexual acts, and yes, Christians should avoid this practice and not condone it, but they should also get equally upset at those people that visit fortune tellers, disrespect their parents, commit adultery, or abuse alcohol.
Within Islam, the Qur'an has much less to say on the subject,
and the Hadith attributes to Muhammad: If a man
comes upon a man then they are both adulterers.
, and
If a woman comes upon a woman, they are both
Adulteresses.
.
Nevertheless, homosexuality is condemned much more strongly than
simply equating it with adultery would suggest,
with six modern Islamic countries requiring the death penalty
for its practitioners.