Mary is a mediator?
The Bible calls Christ the sole mediator between us and the Father. Mary leads us to Christ and intercedes for us, in the same way your pastor is probably trying to, except she succeeds and he fails. Consider this:
I desire therefore, first of all, that supplications, prayers, intercessions, and thanksgivings be made for all men: For kings, and for all that are in high station: that we may lead a quiet and a peaceable life in all piety and chastity. For this is good and acceptable in the sight of God our Saviour, Who will have all men to be saved, and to come to the knowledge of the truth. For there is one God, and one mediator of God and men, the man Christ Jesus: Who gave himself a redemption for all, a testimony in due times (1 Timothy 2:1-6)
Observe: prayers of intercession are urged in the same paragraph as the statement that Christ is "one mediator".