I like to quote Pius X on this one.
From Pascendi Dominici Gregis:
Once indeed We had hopes of recalling them to a better sense, and to this end we first of all showed them kindness as Our children, then we treated them with severity, and at last We have had recourse, though with great reluctance, to public reproof. But you know, Venerable Brethren, how fruitless has been Our action. They bowed their head for a moment, but it was soon uplifted more arrogantly than ever. If it were a matter which concerned them alone, We might perhaps have overlooked it: but the security of the Catholic name is at stake. Wherefore, as to maintain it longer would be a crime, We must now break silence, in order to expose before the whole Church in their true colours those men who have assumed this bad disguise.
The fact of the matter is...
THEY ARE NOT CATHOLIC... destroying the Church from within.