Well, actually the Document that declare Mary to be Immaculate does not declare the unbeliever to be damned. It is required for all Catholic faithful to believed. It is no different than the belief of the Trinity.
Let me quote you the entire context of the Document. The document is called Ineffabilis Deus written in 1854 by Pope XI.
Look at the document yourself and it made no mention of damning anyone who doesn’t believe in it.
papalencyclicals.net/Pius09/p9ineff.htm
I have no idea where you get this Anti-Catholic bias you have. I’m pretty sure the Magisterium of the Catholic Church has look into this dogma seriously. It is part of the deposit of faith. Prior to this, as early as the 3rd Century, the Early Church Fathers believe Mary to be sinless, pure.
The document doesn’t damn anyone but does made this statement.
This of course pertains to the Catholic faithful, not Non-Catholic Christians. The statement doesn’t say that the Church damned you, rather, the man who doubt this belief condemned himself, not the Church.
Get your facts straight my friend.