Jesus sent 72 followers ahead of Him, two by two, to prepare the way for His arrival (Luke 10:1-4).  He warned them that there would be one of two reactions: welcome or resentment.  They could only minister as far as the people wanted them to, and Jesus did not teach that blessings ought to be forced upon resistant or rebellious people.  Indeed, the urgency of the task meant that they should not waste time on those who had no interest.

The public declaration against those who resisted the gospel messengers seems rather harsh.  But it was a prophetic warning, consistent with that of the Old Testament prophets and the Lord Jesus Christ (Luke 11:37-52).  For such rebellious people, instead of announcing salvation, peace and blessing, the messengers were to be heralds of judgement and misery to come.  By using Sodom as being more virtuous than those who reject Jesus, coupled with wiping the dust off their feet, the Eastern symbol of disgust, Jesus was saying that refusal to welcome Him is to exclude themselves from His kingdom and His heaven (Mark 10:32-33)  

Of course, those two messages were the sum of the gospel message - welcome Jesus and His salvation or you will have to face Him in judgement on the final Day (John 3:18).  The purpose of every prophetic warning is that people will repent and trust the Lord (2 Peter 3:9).

Gospel ministry today rarely shows such 3-D clarity.  Either we fail to announce Jesus clearly, or we fail to demonstrate the glorious grace of the gospel; or we spend so much time trying to persuade the disinterested that we miss opportunities to announce the gospel to those who are spiritually hungry.  Very rarely are we straightforward enough to explain that the gospel is not a consumer item (a 'take it or leave it' option which has little consequence) because those who refuse to entertain the message of salvation are on a road to destruction, and they need to be alerted to their danger.  Therefore, there is great urgency - not just for the messengers, but also for their hearers.  Pray that the Lord will sharpen your personal sense of responsibility to work with Him in announcing that Jesus is coming back, and all need to be ready to meet Him.