NC, I don't necessarily think you just too the JWs word for antipathy for Catholics. It does seem to be an interesting exception to the process by which nearly everything else they taught has been rejected. So many xJWs still hold that anti-Catholicism -- that's interesting to me. Could be, stopped clocks are right twice a day, etc.
Or, it could be the general idea I have been suggesting here for a while now: Jw-ism is a thing that tends to attract certain personality types. When people leave the JWs, they don't change their personality; they remain who they always have been. I don't view that as a controversial idea, everyone has their own stories about how difficult it is to stop thinking like a JW -- down to things like their vocabulary.
If JW-ism tends to attract anti-religious, utopian, Manichean types, then you would expect to find certain political and religious viewpoints to obtain whether these are JWs or xJWs. Certainly, you could expect to find antipathy toward the Church, which is religious, anti-utopian, anti-Manichean.
Of course, in any population of sufficient size, you'd expect to find considerable variation in these attitudes. But at least they are testable hypotheses: we could do a test to find whether anti-Catholic attitudes are more deeply felt among XJWs than among the population at large and correlate them with the attitudes toward Catholics among current JWs.