I doubt CynicalBear could answer your questions.
You wrote:
“What was Collyridianism ?”
A heretical movement in Arabia in the 5th century which worshiped the Virgin Mary as god.
“What exactly did the Collyridians do that they were considered heretics ?”
They worshiped Mary as god. Thus, they were excommunicated - and that would happen to anyone who did that today as well.
Well, maybe we should break it down. Let’s take the prayer of Prayer of Pope Pius XII. [http://catholicism.about.com/od/tothevirginmary/qt/Honor_Immacula.htm]
I’ll use just the bolded excerpts from the prayer.
we cast ourselves into your arms
1 Peter 5:7 Casting all your care upon him; for he careth for you. (When did we need to replace God with Mary?)
confident of finding in your most loving heart appeasement of our ardent desires, and a safe harbor from the tempests which beset us on every side.
Hebrews 4:15-16 For we do not have a High Priest who cannot sympathize with our weaknesses, but was in all points tempted as we are, yet without sin. Let us therefore come boldly to the throne of grace, that we may obtain mercy and find grace to help in time of need. (once again Catholics replacing Christ with Mary)
O crystal fountain of faith
Romans 12:3 according as God hath dealt to every man the measure of faith. or "a measure of faith." (but Mary is the “fountain of faith” for Catholics)
Lily of all holiness
1 Samuel 2:2 There is none holy as the LORD: for there is none beside thee: neither is there any rock like our God. (for Catholics however, “all holiness” is given to Mary)
Conqueress of evil and death
Hosea 13:14 I will ransom them from the power of the grave; I will redeem them from death: O death, I will be thy plagues; O grave, I will be thy destruction: repentance shall be hid from mine eyes. (but Catholics claim it was Mary who conquered death)
Convert the wicked
John 16:7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you. 8 And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: 9 Of sin, because they believe not on me; (Catholics have even replaced the Holy Spirit with Mary)
Statement by catholic Bishop Liqouri “.......We often more quickly obtain what we ask by calling on the name of Mary than by invoking that of Jesus.....” She...is our Salvation, our Life, our Hope, our Counsel, our Refuge, our Help”
Mary is their salvation? If that’s not worship and blasphemy I don’t know what is.
Need I go on? Catholics have replaced virtually every attribute and working of God and given that to Mary in their worship.
So in other words the Collyridians where heretics because they attributed to Mary that which belongs to God .
So anyone who ascribes to Mary that which belongs to God is a heretic right ?
(BTW it was this group that Mohamed got the idea that the Trinity was The Father , The Son and Mary from and parts their gnostic gospels are quoted in the Koran)
Say if you gave Mary titles and duties that actually belong to the Holy Spirit that would make you a heretic right ?