Well, and here’s why I think this sneak peek bothers me so much. It’s completely understandable that Henry would feel and think this way. He’s an idealistic child who genuinely believes that good will always win and that blind faith is a good basis for decision-making. That’s realistic and endeering for a child to think, but that hasn’t been shown to be realistic, both in reality and even in the context of the show. Nevertheless, the Charming family gets the special snowflake treatment from the plot quite a bit and I have a bad feeling the writers are going to validate Henry’s view as being the moral one, and the right one. That’s going to make me throw up a little in the mouth.
We don’t know quite how dangerous Cora is, and we don’t know what her overall motivations are other than getting revenge on Regina and Rumple and probably gaining some sort of control. We did, however, see her single-handedly kill every single last survivor in FTL (and possibly the other magical worlds) and reanimate their corpses. And, there seemed to be not a small amount of people in that safe haven. So she’s capable of that, at least. Also, again, assuming that Rumple and Regina are being genuine, they both seem to be pretty desperate to keep Cora back. These are two characters who have spent last season backstabbing each other and being cocky about their own powers and abilities. For them to work together indicates to me that they are pretty seriously worried about Cora getting into Storybrooke.
Also, again, it’s a pretty reasonable assumption for them to make that Cora would beat Snow and Emma. After all, neither of them had too much trouble in the past easily disposing of less powerful, or non-magical people in their way. (Graham, Fairy Godmother, etc). Cora is at least as powerful as they are. Honestly, one of the large reasons why Regina kept failing to permanently separate Snow and Charming was because Rumple needed them to be together for his own purposes and kept interfering with her plans. He’s a large reason why they keep finding each other. Henry’s certainty that Snow and Emma will come out on top is entirely based on an unreliable worldview, and faith. I guess I generally dislike making major decisions affecting large numbers of people on the basis of faith, but your milage may vary on that one. And as for his belief that “good always wins,” which he bases off the curse breaking, as far as I’m concerned, that was not an example of “good” winning. It was an example of Regina not fully understanding her own curse and getting outmaneuvered by Rumple to cast a curse purposefully designed to have a powerful escape clause that he personally made sure to tell Snow and Charming about. If Rumple wanted to create a curse without an escape clause, I’m fairly sure he could have done so. So honestly, at this point, all Regina should know is, “don’t underestimate other powerful people.” Which, incidentally, is exactly what she’s doing in sealing the portal. Again, I know that Henry doesn’t know that. But, if the show writers act like Henry’s view is somehow a reasonable viewpoint for anybody to make large-scale decision on, I’m going to cringe.