Christianity also emphasises righteousness. Homosexuality is a sin. Those who practice it will spend eternity in hell. It's compassionate to warn people who are on that path.

(1 Corinthians 6:9-11 NIV) Do you not know that the wicked will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor male prostitutes nor homosexual offenders {10} nor thieves nor the greedy nor drunkards nor slanderers nor swindlers will inherit the kingdom of God. {11} And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.

(Romans 1:18-32 NIV) The wrath of God is being revealed from heaven against all the godlessness and wickedness of men who suppress the truth by their wickedness, {19} since what may be known about God is plain to them, because God has made it plain to them. {20} For since the creation of the world God's invisible qualities--his eternal power and divine nature--have been clearly seen, being understood from what has been made, so that men are without excuse. {21} For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened. {22} Although they claimed to be wise, they became fools {23} and exchanged the glory of the immortal God for images made to look like mortal man and birds and animals and reptiles. {24} Therefore God gave them over in the sinful desires of their hearts to sexual impurity for the degrading of their bodies with one another. {25} They exchanged the truth of God for a lie, and worshiped and served created things rather than the Creator--who is forever praised. Amen. {26} Because of this, God gave them over to shameful lusts. Even their women exchanged natural relations for unnatural ones. {27} In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion. {28} Furthermore, since they did not think it worthwhile to retain the knowledge of God, he gave them over to a depraved mind, to do what ought not to be done. {29} They have become filled with every kind of wickedness, evil, greed and depravity. They are full of envy, murder, strife, deceit and malice. They are gossips, {30} slanderers, God-haters, insolent, arrogant and boastful; they invent ways of doing evil; they disobey their parents; {31} they are senseless, faithless, heartless, ruthless. {32} Although they know God's righteous decree that those who do such things deserve death, they not only continue to do these very things but also approve of those who practice them.