Rightfully so they point out that Christ coming in His glory would not happen until after such an apostasy would take place. What they don't offer is any sort of interpretation for the second half of vs. 3 and vs. 4. as well as the following verses....2 Thes 2:1-3
1 Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,
2 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
3 Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition;
4 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
Satan has been named perdition. (D&C 76) Those that become his sons are described below...5 Remember ye not, that, when I was yet with you, I told you these things?
6 And now ye know what withholdeth that he might be revealed in his time.
7 For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.
8 And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming:
9 Even him, whose coming is after the working of Satan with all power and signs and lying wonders,
10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
11 And for this cause God shall send them strong delusion, that they should believe a lie:
According to Joseph Fielding Smith in General conference of 1958 October, pg 21....
So I ask you...has this prophecy regarding the son of perdition sitting in the temple been fulfilled? What historical event can you point to for it's fulfillment? If it has already happened...how can that son of perdition be destroyed with the brightness of his coming as found in vs. 8?"...no man can become a son of perdition until he has known the light....it is only those who have he light through the priesthood and through the power of God and through their membership in the Church who will be banished forever from His influence into outer darkness to dwell with the devil and his angels"
Paul wrote his letters to Thessalonica about 50 or 51 AD. The temple of Herod only stood until 70 AD. So it would have had to have been in that 20 year period. If it didn't happen then...then it is to happen in the future.
This individual will be a member of the church with access to the temple who will "deceive the very elect" with his "signs and wonders". It is us who must not "let any man deceive us by any means".
If desired I have other ancillary scriptures that support this claim. Let me know if I have misjudged it somehow...I search for the truth....not just to be right.