Scripture please - chapter and verse, which claims this. Until then, there are a couple of useful statements. If you follow the words of Christ, then you are Christian. If you follow the words of Paul, then you are Paulian. Paulianity has been proscribed as heresy for over a millennium and a half.
I'm sure that to some there is a conflict between Christianity and Paulianty, but with the overall lack of Christian good will displayed by the anti-Catholics I suspect this has nothing to do with religion at all. I think it is filling the void left in their lives by the collapse of racism as an acceptable feel good outlet within their limited culture and circles. There always has to be a "them" to hate and being anti-Catholics doesn't bring down the PC police like hating blacks and Jews.