Only our Lord Jesus Christ can condemn someone to hell. But Christ's servants are given to warn others of that danger, and we are to check ourselves to guard our standing in Christ Jesus. As our Lord said, don't fear those who can kill the body and there's nothing more they can do, but fear Him Who is able to destroy both body and soul into hell (lake of fire) (Matt.10:28).
Concerning those on the pre-trib rapture idea, they are in danger of falling away to the wrong messiah, a warning that our Lord Jesus and His Apostles gave us in His Word. Some on the pre-trib rapture idea will leave that doctrine when they begin to see the endtime events play out differently than what they had been taught. Others will continue to follow it blindly, and will become part of the apostasy Paul warned of in 2 Thess.2 involving a false one coming to sit in the temple of God, to show himself that he is God.
Luke 23:28-30
28 But Jesus turning unto them said, "Daughters of Jerusalem, weep not for Me, but weep for yourselves, and for your children.
29 For, behold, the days are coming, in the which they shall say, 'Blessed are the barren, and the wombs that never bare, and the paps which never gave suck.'
30 Then shall they begin to say to the mountains, 'Fall on us'; and to the hills, 'Cover us.'"
(KJV)
Rev 16:15
15 Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame.
(KJV)
Our Lord Jesus gave that warning to whom? To the wicked that don't know Him? No. To whom then? To those who claim to believe on Him. It is a warning to us to keep our garments so we don't walk naked in shame. The garments are about our white robes from works which follow us to Heaven (Rev.14:13).
Our Lord Jesus warned us about 'a pseudo Christ' (pseudochristos) coming to work signs and wonders on earth and said to not believe on that one. Apostle Paul gave that warning also. Our Lord Jesus made it very plain in His Book of Revelation about that false one who comes first. The Book of Daniel also gives us warning about the final antichrist coming in the last generation.
So it's not like our Lord Jesus didn't warn us already, for He has. None of those who claim to believe on Him will have excuse in mistaking the coming pseudo-Christ that will appear on earth first, working great signs and miracles that would deceive even Christ's elect IF it were possible for His elect to be deceived. Those on the pre-trib rapture theory are taught none of that will affect them, since that doctrine is about the idea of flying away to Heaven prior that pseudo-Christ showing up. That doctrine's preaching that there's a coming by Christ to rapture them to Heaven prior to the tribulation is a direct play into the pseudo-Christ's hands, for that is who the instigators of that doctrine are going to be saying is our Lord Jesus come to rapture us away. Instead, we are to wait for Christ Jesus' coming after that pseudo-Christ does his thing.