I can actually provide you (and the mod if needed) with links by PM (I have saved a lot of my postings, etc.) to posts by Catholics that made like comments, including that Protestantism is a false religion, belief in one’s self, who have no faith in Christ, no foundation for their superficial understanding of Christianity, who are by inclination vandals, evil fruit, ignorant, biblically illiterate, typically intellectually dishonest, absolutely alien to Christianity, a false religion, a bizarre and false religion, a mass of sheer rot, a heretical brand of Christianity, who completely reject Christ, belief in one’s self, with no foundation for their understanding of Christianity, and who are unable to defend it.
And even yet also claim there is not a bit of anti-protestant bigotry among Catholics here, nor that they never belittle or challenge beliefs from protestants, incldg. threads of Catholics initiating an argument with protestants.
If you can find one dumb in-DUH-vidual who did say that (and since you have extensive archives, perhaps you will find that errant FReeper who is guilty as charged) they were not saying anything found in the Catechism of the Catholic Church, which is a reliable summary of what the Catholic Church teaches. So they may be Catholics, but were not speaking "as Catholics."
As for Protestants holding religious errors: yeah, but that's not necessarily imputable as a damnable heresy. There were blessed Doctors of the Church who were in error about one thing or another, but not as pertinacious heresy. Some of them had gaps in their knowledge. I daresay everybody does.
Or it may be a matter of interpretation. Even James said one is not saved by faith alone. Whatever he meant by that!
My favorite was calling Protestants “Paulistinians” back when several RC’s were calling the Apostle Paul a nut.
I think you're thinking of the same Freepers I'm thinking of. ;o)