This article and this article will help you appreciate and understand the background of this singular privilige granted to Mary, the mother of Jesus (and, since Jesus is God, the Mother of God) --a privilige granted to her not because of Mary's own merits or glory, but because if it's fittingness in relation to her role as Mother of Our Redeemer (like all of the teachings of the Church about Mary, the doctrine says more about the uniqueness and holiness of Jesus than it does about Mary).
If, however, you find yourself in the position of having to explain this wonderful Christian truth, here is a helpful article from Catholic Answers. It answers the questions:
1. Why does the Church teach that Mary was immaculately conceived? Her conception is never even mentioned in Scripture.
2. If Mary is sinless, doesn’t that make her equal to God?
3. How could Mary be sinless if in the words of the Magnificat she said that her soul rejoices in God her savior?
4. How can you reconcile Mary’s sinlessness with Paul’s statement that all have sinned and fall short of the glory of God?
5. Didn’t the Church just invent the doctrine 150 years ago?
This article may also be helpful.
To misunderstand a concept is to fear and hate it, but to know the truth often leads one to love it. Be ready when your questioning friends and families are looking for answers and help lead them from fear and hate, to truth and love.