Matthew 7
7 “Judge not, that you be not judged. 2 For with what judgment you judge, you will be judged; and with the measure you use, it will be measured back to you. 3 And why do you look at the speck in your brother’s eye, but do not consider the plank in your own eye? 4 Or how can you say to your brother, ‘Let me remove the speck from your eye’; and look, a plank is in your own eye? 5 Hypocrite! First remove the plank from your own eye, and then you will see clearly to remove the speck from your brother’s eye.
You do know that the correct measure to judge by is the word of God, no?
This is in the same chapter:
The Narrow Way
13 “Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it. 14 Because narrow is the gate and difficult is the way which leads to life, and there are few who find it.
and this:
21 “Not everyone who says to Me, ‘Lord, Lord,’ shall enter the kingdom of heaven, but he who does the will of My Father in heaven. 22 Many will say to Me in that day, ‘Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?’ 23 And then I will declare to them, ‘I never knew you; depart from Me, you who practice lawlessness!’
You do know Jesus spoke more about hell than heaven no?
So in other words, no, you have no verses that state not to warn others about hell.