Why would God send a deluding influence on people so they would believe what is false? Isn’t that morally wrong? First of all, let’s look at the context.
2 Thess. 2:8-12, “And then that lawless one will be revealed whom the Lord will slay with the breath of His mouth and bring to an end by the appearance of His coming; 9 that is, the one whose coming is in accord with the activity of Satan, with all power and signs and false wonders, 10 and with all the deception of wickedness for those who perish, because they did not receive the love of the truth so as to be saved. 11 And for this reason God will send upon them a deluding influence so that they might believe what is false, 12 in order that they all may be judged who did not believe the truth, but took pleasure in wickedness.”
Verses 8-9 are speaking of the arrival of the antichrist. Verse 10 speaks about those who rejected the truth. Verse 11 says for this reason God sends a deluding influence on them so they would believe what is false.
Paul is telling us that God will send a deluding influence to those who are already rejecting the truth (v. 10), so they would believe what is false regarding the coming antichrist. God isn’t sending a deluding influence upon those believing the truth, but upon those who reject it. This isn’t wrong since they are already believing what is false. Their judgment is right because they did “not believe the truth, but took pleasure in wickedness,” (v. 12). It’s like God saying, “You want to follow lies and wickedness? Okay, so be it. Believe your lies!”
This is the same as God judging those who reject his truth by giving them over to the lusts of their hearts (Rom. 1:24), their degrading passions (Rom. 1:26), and their depraved mind (Rom. 1:28). God judges the hearts and minds of people so that they will be strengthened in their rebellion. He gives them more of what they want, and their coming judgment is proper.
God has the right to execute judgment upon all who would believe lies and seek wickedness.