They still need to excommunicate Hitler.
If someone is already dead he/she can't be excommunicated.
So to the pope Hitler is in heaven enjoying the fruits of all the Jews which died by his hands.
No...
Well, I'm not interested in "defending the catholic church" (and I didn't mean to do that with my previous post) and since I'm quite shy and my english sucks, but I can tell you that the "purpose" of excommunication is not to declare "directly" that a specific person or a group of people "will go to hell, and that's it". Therefore not excommunicating someone, even if he's the incarnation of evil, doesn't mean they think that "he's going to heaven" at all as you suggest above.
Anyway both my english and my knowledge aren't good enough to talk about details of excommunications and I'm sure nobody here is interested in them so...
I just wanted to point out that the fact that a dead person can't be excommunicated has a lot to do with the original purpose of excommunication and the fact that they didn't excomunicate Hitler when they could is indeed quite shameful.