It really is a shame that the Catholic church has gotten such a bad rap due to the misguided actions of a few individuals. Something like that is hard to fight though. Not to mention the nice witch and Protestant roastings they had too.
In all seriousness, I know many Catholics who have a deeply fulfilling spirituality. I think the difference is that these people took the time to learn exactly why they're engaging in these rituals and to give them a personal meaning. Overall, I think Catholicism as a social institution produces relatively few of these sorts of people due to various flaws in the system or teachings. Hence the large amount of "recovering Catholics" you'll find, especially in the US.
But I digress. I would also like to point out (as the dork historian that I am) that the term Heirophant does not have a specific Catholic heritage. In fact, High Priest strikes me as more structured than Heirophant. The term Heirophant is most often used in conjunction with an ancient religious group who engaged in the Eleusian (sp?) mysteries dedicated to the goddess Demeter, who is the Greek goddess of grain and fertility. Unfortunately, the group was very good at keeping their secrets so nobody knows with any real depth what they did. But we do know that the Heirophant initiated people into the mysteries, and there was some sort of secret knowledge revealed that was supposed to save the initiate.
Perhaps it will make it easier for those who do not like Catholicism to think of the Heirophant in those terms? As far as interpreting the card goes, I think of him as the ancient heirophant of the mysteries. He is someone who passes down the collected knowledge of the ages. He also teaches the societal rules of how to interact with others. Some see this as a restrictive function, but it doesn't necessarily have to be that way. Knowledge of the ways of societies and religions is only as restrictive as you let it be, and let's face it, knowing the social rules of a society can stop you from a lot of embarassment.
Just a few (okay, a lot) of thoughts.