In Jesus' day, there were two religious/political parties in Israel: the Pharisees and Sadducees.  They were politically important because they held the majority of seats in the Sanhedrin - the highest religious court which, later that week, would 'try' Jesus.  Pharisees believed it was important to keep all the small details of the Jewish Law because God would call them to account when He raised the dead.  But Sadducees did not fully accept the authority of God's Word and did not believe that there was any life after death.  

Some of these Sadducees put a riddle to Jesus about Levirate marriage (the duty of a man to marry his brother's widow if she had no male children to own the family land - Deuteronomy 25:5-6).  As they represented the landowning aristocracy, they had no problem at all with the principle of Levirate marriage.  However, they wanted to force Jesus into declaring that He believed in the resurrection even though it seemed an illogical idea to them.  They had no interest in finding the truth.  Their objective was to remove His authority by ridiculing His logic.  They arrogantly thought that Jesus could not deal with their question, and in Middle East culture the argument is won when one side falls silent.

People, who have no assurance of resurrection to a new life with God, will always be uncomfortable with those who do.  Their discomfort may be expressed as ridicule if they feel threatened by other people's faith in Jesus.  They may ask all sorts of questions, not because they are interested in knowing the answers, but in order to disable the Christian's certainty and make themselves feel better.  

Alas, if you do not believe that God will call all people to account, then feeling good about yourself and helping others to do the same is the best thing you can do.  But when you do believe in the resurrection of the body and are confident of eternal life, then you know that everything in the present has a purpose because it will be evaluated by Jesus.  So, remember to make today count for eternity; we are here to please Jesus (2 Corinthians 5:9)!