I'm sorry but that is just more nonsense and misrepresentation.
Christianity had a history going back hundreds of years before Constantine of taking existing holy days, traditions and holy sites of other religions and incorporating them into Christianity. Even Paul used that tactic.
The Council of Nicaea did not centralize the Bishopric and in fact recognized that both the Bishop of Jerusalem and Alexandria would hold position of priority.
Constantine had nothing to do with Christianity adopting Sunday as their Sabbath; that was done by Christians to help differentiate themselves as a separate religion and not just another Jewish sect long before Constantine.
Easter is simply the adoption of Passover from the Jews and came long before Constantine.
Christmas is simply the adoption of the Winter Solstice.
Pentecost was simply Christianity adopting Shavout.
Have you ever read the Bible or studied anything about Christian history?
Anyone so limited that they can only spell a word one way is severely handicapped!