Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, 10 nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God.
First up, this passage isn't saying that anyone who has ever stolen or been drunk will not inherit the kingdom of God. What it is saying, is that people who unrepentantly practice these sins are not saved. Unrepentant adulterers, thieves, greedy people, and yes, homosexuals will not inherit the kingdom of God. A similar passage, 1 Timothy 1:9-11, is similar to that passage:
understanding this, that the law is not laid down for the just but for the lawless and disobedient, for the ungodly and sinners, for the unholy and profane, for those who strike their fathers and mothers, for murderers, 10 the sexually immoral, men who practice homosexuality, enslavers, liars, perjurers, and whatever else is contrary to sound doctrine, 11 in accordance with the gospel of the glory of the blessed God with which I have been entrusted.
This next passage from Romans shows that homosexuality is a “dishonorable passion” that's a judgement from God on wickedness:
For this reason God gave them up to dishonorable passions. For their women exchanged natural relations for those that are contrary to nature; 27 and the men likewise gave up natural relations with women and were consumed with passion for one another, men committing shameless acts with men and receiving in themselves the due penalty for their error.
28 And since they did not see fit to acknowledge God, God gave them up to a debased mind to do what ought not to be done.
Two more passages that strongly proclaim the sinfulness of homosexuality are found in Leviticus:
If a man lies with a male as with a woman, both of them have committed an abomination; they shall surely be put to death; their blood is upon them.
You shall not lie with a male as with a woman; it is an abomination.
People will argue that because this is in the Mosaic Law, it doesn't apply to us today. However, look at the second part of both of those verses again: one says “both of them have committed an abomination”, and the other states “it is an abomination”. Yes, this is in the Law, and I am a strong believer in the fact that we don't have to obey the Mosaic Law anymore as evinced in Galatians 5:18 among other passages:
But if you are led by the Spirit, you are not under the law.
However, the fact that homosexuality is an abomination in God's sight has not changed. In fact, to make the point doubly clear, God states it twice that homosexuality is an abomination to him.
You may next ask “Well, does the Mosaic Law say that eating shellfish or wearing clothing made of two types of fabric is an abomination?” Nope. The phrase “it is an abomination” and similar terms (“it is perversion”, “it is depravity”, etc) are only found in chapters of the Law that talk about horrific sexual sins such as incest and bestiality.
Still not convinced? Did you notice that the penalty for homosexuality under the Law was death? God's not going to take something He commanded death for in the Old Testament and say “Oh you can do whatever you want now.”
Now I will add, there most definitely are genuine believers who struggle with the sin of homosexuality, just as there are genuine believers who struggle with other sins like lying or greed or any of the other sins listed in 1 Corinthians 6:9-10 or 1 Timothy 1:9-11. Should we look down on the believers who are actively fighting these desires? Of course not.
Another note: homosexuals aren't worse sinners than any other lost person. What's the best thing you can do to help lost people trapped in this sin? Witness to them just as you would any other lost person. Practicing, unrepentant homosexuals are in need of a Savior more than anything else. =)