Christ wasn't the only one to use such language, although He does it again in Luke 24:25 (and that time it's
not religious hypocrites that He's speaking to).
Maybe Paul
is in danger of hell fire for this slip of the tongue/pen.
I Cor. 15:36 Thou fool, that which thou sowest is not quickened, except it die:
The key to understanding the verse in question is understanding where and when the statement applies. Application is crucial. You've already noticed a problem when trying to apply the statement to Christ's later preaching. Again, you'll find trouble if applying it to the Apostle Paul's letter to Christians in Corinth. So, application is crucial.
Now, where and when does this teaching apply? The answer is in the chapter. As a matter of fact, it's all over the book of Matthew. The kingdom Christ is offering to "His own" is called the kingdom of heaven. The King (vs.35) was present and preparing His people for something that they rejected...and here we are as a result!
The statement in question (as well as those preceding and following) is aimed at the Jews whom Christ was coming to deliver. Forget about their rejection and the cross (hindsight will hinder you from understanding) and notice the message that Jesus Christ originally preached.Matt. 10:5-7
5. These twelve Jesus sent forth, and commanded them, saying, Go not into the way of the Gentiles, and into any city of the Samaritans enter ye not:
6. But go rather to the lost sheep of the house of Israel.
7. And as ye go, preach, saying, The kingdom of heaven is at hand.
As for the application, the statement will be in force when the King comes back and sets up His kingdom. If it's for today, then there's a problem (as you've noticed) with the scripture.