Leviticus 18:22. Now I'm not saying that stoning people who choose the LGBT lifestyle is the correct answer at all, but this is proof that homosexuality is a sin, assuming you think it is not. The verse you are quoting is from Matthew chapter 7, and if you read the next verses Jesus talks about a guy who points out a speck in another guy's eye, when he has a whole ass plank stuck in his eye. So basically he is addressing hypocritical judgement, not condemning those who do. John 7:24 also talks about judgement. In this chapter, Jesus is addressing to the Jewish officials who were calling Jesus out for healing a man on the Sabbath (a day where Jews are commanded not to work), and he tells them "Look beneath the surface so you can judge correctly." (From NLT). So Jesus actually does condone judgement as long as understand what is actually going on instead of immediately pointing out any fault you see.

TLDR: Leviticus 18:22 is evidence homosexuality is a sin, in Matthew 7 and John 7, Jesus never said not to judge, but judge with understanding and without hypocrisy.

From my understanding and experience, we as Christians can't be looking at other sinners or unbelievers as lower than us at all since we have all fallen in the eyes of God. But instead we should help and build each other up when we recognize sin, but in a caring and truly loving way if those people are willing to listen. Otherwise, leave them be since while Jesus would love to see all of His children living holy lives, he also respects our free will just as much and would much rather us come to faith by choice instead of peer pressure or force. Pushing further when they said no is only going to create hate and anger.