Ad hominem. I know well the whole and that is why I rebuke it and condemn it for what it is.
1. Communication with the dead is impossible - Ecclesiastes 9.
2. Attempting to communicate with the dead in every form is outlawed under the laws of God in the OT and assigned the death penalty in all the forms it takes.
3. If it is both impossible to communicate with the dead and a sin unto physical death to do it, then Mary can't hear you and you are committing sin in trying to speak to her - even if it's just to ask a favor.
4. Given 1-3 we have example to back it up. Saul tried to communicate with Samual and God put him to death for it. Thus the statute of god forbidding it, the law of God designating God's penalty and GOD HIMSELF condemning and putting Saul to death for it.
5. Salvation is through Christ and him alone. John 14:6 "Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me."
6. Communication with God is through Christ and Him alone. John 14:6 "Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me." John 10: 7-8 "John 10:7 Then said Jesus unto them again, Verily, verily, I say unto you, I am the door of the sheep. [8] All that ever came before me are thieves and robbers: but the sheep did not hear them.
If you are trying to approach any other way you are a thief and a robber.
7. 1 Timothy 2:5 For [there is] one God, and one mediator between God and men, the man Christ Jesus; [6] Who gave himself a ransom for all, to be testified in due time.
So, not only is it forbidden to speak to the bodily dead. Not only is it impossible. God Gave a mediator through which we may approach him and you violate even that. And Jesus himself stated that No one can approach God but through Him. You have to pray through Christ - not Mary or the Saints - through Christ. You've made Mary a mediator and thusly termed her "mediatrix." Your entire pile of doctrine betrays your church a liar as it stands before the truth of scripture.
You've created another mediator in the persons of Mary and the saints - not just one, but countless. Heresy. You preach that praying or seeking favor from the physically dead is useful and proper - heresy and demonstrated so by the statutes and actions of God on the very subject. And you seek salvation through another mediator, favors through that mediator, etc. Directly in contravention of scripture and as a perversion of it. You teach not only another Gospel; but, a replacement Gospel designed to give lipservice to God and Christ while violating the statutes of both and superceding them with your own. You are thieves and robbers.