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.
Likely disagreed with the Roman Church. That's all it takes to earn the label of *heretic* from them. Fidelity to Scripture doesn't enter into it.
In a nutshell, it means you were right about whatever they labeled you a heretic over.