I totally agree with you. A pre-tribulation rapture theory would give people a license to sin, since most who trust in this theory also believes that once saved always saved can give them that opportunity to "come short of the glory of God," and that when the 'rapture' takes place they will escape the trouble coming upon the earth afterwards.
How many times have you heard phrases like, "I hope the rapture comes today: I won't have to go to work!"? My, oh my. That phrase in itself is a sin! It shows irresponsibility in one's life. Work is something a Philadelphian or Smyrnian should never try to avoid. Good work is what we are supposed to do: it shows trustworthiness and honesty! And that's just one point among thousands that can be said about the pre-tribulation rapture theory.
If you are chosen to endure that day, may you be poured out onto by a double portion of God's Grace and Power to be able to withstand that evil day. And I ask this of our Father, in the Name of the Only Begotten Son of God - The God of Abraham, Isaac and Jacob: The Only One Qualified to shed His Blood for the Remission of our sins, Jehovah Jireh, Christ Jesus My Lord.