You don't have to defend everything about Catholicism. But if I started badmouthing Muslims, saying they all (or most) were backwards, worshiped the Devil, and were terrorists, how might you react? Would you at least encourage me to be fair?
On the other side, if Mrebo were saying something unfair, generalizing about Democrats or something else, or if Vladius (the only self-confessed Mormon other than myself on this board I'm aware of, though I know of two others who'd rather remain anonymous) started speaking badly about Southern Baptists, do you think I wouldn't stand up for the Baptists or the Democrats? If the criticism were legitimate, I wouldn't have a problem (though I'd encourage, forcefully if necessary, a better tone that would promote discussion if they were typing in such a crass manner as HotRod). But HotRod was not accurate, not fair, and spoke in an extremely disrespectful manner. You don't have to like many of the things the Catholic Church has done, many of their teachings, many of the actions of individuals, but to brand all Catholics the way he has is the very definition of bigotry and stereotyping.