ttg, I'm not sure what the root cause is, myself. I was once one of the anti-Catholics, to the point of personally ridiculing people, believing that history had been altered through a Catholic Church conspiracy, etc. But, even at my rudest and most hateful, the Holy Spirit was speaking to me the loudest in my heart. It was a hard shell to crack and it took me months to even admit to anyone the truth. I am even guilty of denying my belief to avoid ridicule among protestants. I am ashamed of that and of my prior attitude toward Catholics.
I know I grew up here in Texas, the south, in the Baptist/Methodist Bible Belt. I pretty much grew up with implicit distrust of Catholics, who I was taught were not Christians, were worshipping Mary, who couldn't talk straight to God (but had to use a priest), who had church on Saturdays (not really sure why I was taught that -- it just shows the core level of ignorance being taught to Evangelical/Fundamentalist children by their equally uninformed parents), who had strange worship styles, etc... After all, WE don't KNEEL in church, why do THEY?... Why do they use REAL WINE?! The drunkards! I was taught that Catholics get drunk in church and dance on the tables in their fellowship (parish) hall, and that they cuss and sin and generally are a disgrace to Christians and that they dont' believe in the Bible and that they kept the Bible away from people and wouldn't let anybody else read it, etc. etc. I was taught these lies and a good portion of people on this board were and a larger portion of Evangelical/Fundamentalists believe these things, because it was what they have been taught for several generations, as a way to discredit Catholics, a bigotry that goes so far back that no one in their family really remembers where it started and it is taught either explicitly or implicitly in most of the churches. Even the big mega non-denom church I went to for a while, who runs TV spots and has 15,000/week attendance... they run ads where they say things like "we just believe that church should be an experience that is fun for the whole family" or "we don't believe in religion" etc. It's implied, but it's clear, especially if you're tuned into it. For those that aren't tuned in to it, it passes by, but still enters the mind, the subconscious, the attitude.
I love my Christian brethren. I defend the Catholic Church, because I believe in it the way you believe in your particular theology. We both feel the other is wrong, but the name-calling and insults are pretty non-Christian if you ask me.
-Michael