Unlike some, I don't think this is a particularly big Catholic story. The St. Patrick Day parade long ago ceased to be any kind of religious procession, to the extent it ever was more a religious event than an ethnic celebration for a group which happens to be, in origin, mostly Catholic. The Grand Marshal role is a ceremonial one and has been extended to the Cardinal as a courtesy. I don't think that the Cardinal is obligated to turn down the honorary position because of this latest devolution in the parade, but I do agree with Msgr. Charles Pope's (since pulled but linked to here via Google cache) post saying that he ought to. The diocese's involvement with the parade at this point does nothing to raise the parade, and a certain amount to lower the diocese.
This isn't exactly unfamiliar territory. Read a bit about the history of the various festivals, plays and parades of the medieval church, and it seems like such things followed a cycle. First they served a real purpose, giving a faithful a way to celebrate and learn more about their faith. Then they simply became fun. Then they became actively debased and the clergy started trying to stamp them out again. Rinse and repeat. There seems to be a natural course of things which, on this event, we find ourselves at the end of.
Scalia, in her above linked post, seems to imagine that the Cardinal is performing some kind of evangelization. She links his actions with those of the father in the Parable of the Prodigal Son, a parable so constantly mis-used that it begins to seem that someone should draft one of these online laws of discourse in which you immediately lose when you cite it. She says:
Well, the Saint Patrick’s Day Parade has, at least in New York City, long been a trooping of the sinners, but let’s think for a moment about those muddy circumstances, again, and the story Jesus told, the parable of the Prodigal Son.They key is actually that in the story of the prodigal son the son is returning. There's no indication of return, for any reason, in this situation and in many in which the parable is invoked.
Recall, the wastrel son of a rich man asked for his inheritance, and then he squandered it so thoroughly that he was stuck feeding the pigs, and growing hungry. The son thought,
“How many of my father’s hired workers have more than enough food to eat, but here am I, dying from hunger. I shall get up and go to my father and I shall say to him, ‘Father, I have sinned against heaven and against you. I no longer deserve to be called your son; treat me as you would treat one of your hired workers.”’Reread the last two sentences. It didn’t matter why the son was seeking inclusion; the father did not know whether he was coming home repentant or full of swagger. Motivation did not matter. And the son was still a long way off. All the father knew was that the son had made a move toward home, and it was enough to send the father running out, to meet him.
So he got up and went back to his father. While he was still a long way off, his father caught sight of him, and was filled with compassion. He ran to his son, embraced him and kissed him.
I’m not sure a bishop has a choice but to run out to meet prodigals, regardless of motivating factors. The father wants everyone to come home and be with him. Once they’re at the doorstep, they may be encouraged to come in; once they’re inside, they can be talked with, nurtured, fed, encouraged, formed, and made whole. This cannot happen as long as they are off in the faraway places.
The key here, aside from the father running out to the prodigal son, is that he ran out while the son was still a long way off.
Jesus could have told a parable in which the father went and ran after the prodigal son's party set shouting, "Hey guys! Hey guys! Can I come too? I'm a cool guy too!" and imagined that perhaps by coming along he would evangelize the party-ers -- using words only if necessary (to paraphrase the famous yet bogus St. Francis quote.) He could have told a parable in which the son comes back, unrepentant, and offers to throw a party at the father's house, making the father an honorary master of ceremonies. He could have told a parable in which the son comes back, the father rushes out to meet him, but the son turns out to only be returning to wash his laundry and borrow some more money.
However, these are not the parables that Jesus chose to tell, and it's kind of useless to speculate on how the parable might have gone and what the lesson might have been had He done so. The parable we actually have is a parable about repentance and how to respond to it. In that parable, the prodigal son comes home with the intention of repenting, and the father welcomes him extravagently, even though it offends his other more upright son. This is how we, as Christians, are called to act. Indeed, failure to thus welcome back the repentant is a sin. It may damn us.
Does this mean waiting until the repenting sinner is behaving just perfectly before letting him in the door -- whether the door to the church or the door to our community? No. Indeed, as a wise friend once pointed out, most converts are heretics for a while. In other words, real people don't go from disagreeing with the Church (in word or in action or both) to being fully faithful over night. They change through a process (whether fast or slow) of conversion. They may not be able to accept the whole truth at once, but even if they think they do, most people don't "get" the whole truth at once, and so even with the most sincere intention of now following the Church's lead, many new and in-process converts don't.
What converts do do, however, is want to follow Christ. What those who repent do do is want to turn away from sin.
Inviting a cardinal to be honorary chair of your event, while you run it exactly as you like, is neither an act of conversion nor repentance. It's just a case of asking a high profile figure to lend his name to your event. He's not required to go along with your request out of some Christian duty to do everything we're asked because that's what the father in the prodigal son did.
No, what the cardinal should do is prudently consider what the best action would be in this case and then do it. And I would submit that it would be prudent to pass up this particular honor on the theory that the St. Patrick's Day Parade long ago ceased to have much of anything to do with St. Patrick, and instead became a festival of green beer (most surely an abomination against God and man) and leprechauns. There's nothing which the Church can do to prevent those who run the parade these days from inviting gay advocacy groups to participate in the it. (Nor were they in the past able to prevent those involved in violent Irish nationalist groups from participating.) But there is certainly no evangelistic value to holding an honorary position of authority in the parade, and no reason to lend the diocese's stamp of approval to activities of which it should not approve.