The disciples did not allow the little children to come to Jesus because they thought that they were just annoyances to the Lord. They did not understand Jesus' message.

The Lord Jesus allowed the children to come to him because to such belong the Kingdom of God. He also wanted to convey a very important message of humility and innocense through them in coming to the God.  

When there is no love but hatred, bitterness, unforgiving controls the heart. 

To avoid, one must learn to walk with Lord Jesus - Love is patient, love is kind. It does not envy, it does not boast, it is not proud. It is not rude, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. Love does not delight in evil but rejoices with the truth. It always protects, always trusts, always hopes, always perseveres. Love never fails.