Homosexuals shall not inherit the kingdom of God?
1 Corinthians 6:9-10 gives a list of those who shall not inherit the kingdom of God. There are two different Greek words in this sentence sometimes translated "homosexual", but there are translation difficulties with both these words.
Various ancient Greek writers discuss homosexual behavior quite a bit, and so we have a good knowledge of what the culture of the time thought about homosexuality and what words they used to describe it. The words Paul uses are not the normal words used to speak of homosexuality.
The first of Paul's two difficult words is "malakos" which literally means "soft" and is a fairly common Greek word that depending on context can mean virtually anything: (1) "soft" grassy meadows, (2) "gentle" or "mild", (3) "cowardly", "lacking self-control", (4) low pitched music, (5) poor logic or reasoning (6) "weak", "sickly". The context of Paul's list is moral vices and so meanings from definition 3 above are appropriate ones and thus "lack of self control" seems best. Some people appear to have decided that the word can mean 'soft' in a sexual sense and thus mean 'effeminate' or 'passive homosexual partner', which I suppose is possible. There seems no reason to think the context here merits such a translation though.
The second of Paul's difficult words is "arsenokoites" (literally "man-bed") which has the opposite problem - this word does not occur enough times in surviving documents for us to tell clearly what it means. The evidence provided by these occurrences is confusing. It appears in some listings of economic sins. Elsewhere it is said to be something mainly done by men with men but which can even be done to a woman. A meaning that explains a lot of the evidence (but not all) is "anal rape" or "having sex with someone in order to prove dominance over them" (bear in mind that in the ancient world this was a somewhat common practice for heterosexuals to engage in). In short, Greek usage provides no reason at all to think that the word means "homosexual". No study I have ever seen has concluded that the word meant "homosexual" in Greek.
However Christians who have studied Greek are rather infamous for never reading or paying attention to any Greek documents outside of the Bible. So often their policy is: Using the Bible alone, what does this word mean? I would like to stress that such methodology, in general, is incredibly bad. The bible was written in Koine ('common') Greek and it uses normal words from the common Greek of the time. It was NOT written in some heavenly language that came into being for the sake of writing the bible and then immediately disappeared (as a few scholars once wildly speculated!). Its original readers when reading it would have understood the meanings of the words it uses because they already knew what the words meant from their knowledge of Greek, just as we who read it in English understand it because we already know how to speak English.
At any rate, people have searched the bible from top to bottom to see what arsenokoites (man + bed) means in the 'bible' language and discovered a passage that uses 'man' and 'bed' in the same sentence in the bowels of Leviticus. Therefore it must be a reference to that, right? (Because, of course, Paul would invent a word his Corinthian readers didn't know and expect them to search the bible from top to bottom to find the sentence that most closely matched it... not!) The sentence in Leviticus is generally believed to be condemning homosexuality and therefore "arsenokoites" in Paul's writings is translated "homosexuality".
In short, I see no reason to think either malakos or arsenokoites in 1 Cor 6:9 have anything to do with homosexuality whatsoever. Such translations are simply a result of poor scholarship.
PS. It has been brought to my attention that a lot of the evidence regarding ancient usage of 'arsenokoites' was only discovered in the last 30 years, and that therefore the scholars who in the past concluded it meant homosexuality based on the above-critiqued argument were engaging in reasonable speculation based on the lack-of-evidence they had at the time.