God has made it clear instruction that he forbids sexually immoral behaviour, including homosexual activity:
1 Corinthians 5:9-12 I wrote to you in my letter not to associate with sexually immoral people– (10) not at all meaning the sexually immoral of this world, or the greedy and swindlers, or idolaters, since then you would need to go out of the world. (11) But now I am writing to you not to associate with anyone who bears the name of brother if he is guilty of sexual immorality or greed, or is an idolater, reviler, drunkard, or swindler–not even to eat with such a one. (12) For what have I to do with judging outsiders? Is it not those inside the church whom you are to judge?
Nevertheless the apostle Paul has instructed us how we should treat all people.
Titus 3:1-2 Remind them to be submissive to rulers and authorities, to be obedient, to be ready for every good work, (2) to speak evil of no one, to avoid quarrelling, to be gentle, and to show perfect courtesy toward all people.
1 Timothy 2:1-4 First of all, then, I urge that supplications, prayers, intercessions, and thanksgivings be made for all people, (2) for kings and all who are in high positions, that we may lead a peaceful and quiet life, godly and dignified in every way. (3) This is good, and it is pleasing in the sight of God our Savior, (4) who desires all people to be saved and to come to the knowledge of the truth.
The Bible does not say that we should only treat people well if they lead a Christian lifestyle. God calls all sorts of people to repentance.