I think that “Consider all the European Catholics who are essentially atheists” should be read as “Consider all the {European Catholics who are essentially atheists}”, not “Consider {all the European Catholics}, (who are essentially atheists)”.
I think that “Consider all the European Catholics who are essentially atheists” should be read as “Consider all the {European Catholics who are essentially atheists}”, not “Consider {all the European Catholics}, (who are essentially atheists)”.