People who believe in a post-tribulation rapture offer several arguments against a pre-tribulation rapture. Listed below are some answers to their arguments.

In the Old Testament, there were two different pictures painted of the Messiah—one suffering (Isa. 53:2-10, Ps. 22:6-8, 11-18) and one reigning as King (Ps. 2:6-12, Zech. 14:9,16). As we look back on these Scriptures, we see they predicted two separate comings of the Messiah—the first coming as a suffering Messiah and the second coming (still future) as a reigning King.

In the New Testament, we have another picture added. Again, we have two pictures painted and they don’t match. These two descriptions of Jesus’ coming point to two separate events we call "The Rapture" and "The Second Coming." (see "The Rapture vs. The Second Coming" Bible study)

Answer: This is not the rapture for several reasons:

1. Christians will receive resurrected bodies at the rapture (1 Cor. 15:51-53). If we are in resurrected bodies like Jesus, we will be able to ascend just like Jesus did when He ascended (Acts 1:9). Why would we need angels to gather us when our bodies will have the same capabilities as angels (Matt. 22:30)? Obviously, they are gathering the elect, those who have been saved after the rapture who are in their natural bodies.
2. The angels also gather the wicked at this time (Matt. 13:38-43, 49-50).
3. If you make the argument that the angels gathering the elect in Matt. 24 is the rapture, then you will also have to claim the angels gathering the wicked in Matt. 13 is also the rapture. Of course, no one believes the wicked are raptured at the second coming.
4. The angels are sent forth to gather both the righteous and the wicked together for the judgment of the nations (Matt. 25:31-48). These are all people in their natural bodies. The wicked will be cast into the lake of fire, while the righteous will enter into the millennial kingdom.

The last trump is a term used for the last trumpet blown during the Feast of Trumpets. The rapture will be the fulfillment of the Jewish Feast of Trumpets:

"The 'last trump' refers to the Feast of Trumpets and the Jewish practice of blowing trumpets at this feast each year. During the ceremony, there is a series of short trumpet blasts of various lengths, concluding with the longest blast of all, called the tekiah gedolah: the great, or 'last trump.' Judaism connected this last trump with the resurrection of the dead, and so does Paul. So, Paul's point here is that the Rapture will be the fulfillment of the Feast of Trumpets. [Arnold Fruchtenbaum, "A Review of The Pre-Wrath Rapture of the Church" (Tustin, CA:Ariel Ministries), p.58]

No one (that we know of) who holds the pre-tribulation rapture position has ever said Christians will escape persecution. Jesus said the world would hate us (John 15:18). The rapture will occur at a separate time than the second coming because God has different programs for the Church and Israel. God has not destined the Church for the wrath that will be poured out during the tribulation (1 Thess. 5:8).

Paul is speaking of the day of the Lord (the Tribulation), not the rapture. Paul is showing the relationship between the rapture (v.1) and the day of the Lord (v.2).

First, the day of the Lord refers to the The Tribulation period, not the rapture.

The "day of the Lord" doesn't mean a 24 hour day, but a time period of judgment (Isa. 2:12, 13:6,9, Ezek. 13:5, 30:3, Joel 1:15, 2:1,11,31, 3:14, Amos 5:18, 20) The Thessalonians were shaken and disturbed because someone had deceived them into believing the Tribulation Period had begun. Paul said the antichrist must be revealed before this happens. When the antichrist confirms a covenant with Israel, he will be revealed, beginning the 7 year Tribulation period.

Second, if the Thessalonians believed in a post-tribulation rapture, shouldn't they be rejoicing?

If the Thessalonians had been taught a post-tribulation rapture, they would have been rejoicing because the beginning of the Tribulation was evidence the post-tribulation rapture was near. They wouldn’t be disturbed or alarmed because this is what they would have expected--to go through the Tribulation.

But we find the Thessalonians were disturbed. Why? Because if the Tribulation period had begun, it meant they missed the rapture. This is why Paul writes them about the rapture (v.1), then explains that the Tribulation period begins when the antichrist is revealed. Because that hadn't happened yet, they didn't miss the rapture.