Information can often be important. But the simple fact is that it comes down to a really basic cost-benefit analysis.
Do you take prisoners in the heat of battle? The answer is no. Yes, he was already tied up, but as has been mentioned several times already, taking any time to watch him is time better spent elsewhere. Several lives may have been saved by Morgan.
Do you take prisoners when you may be outnumbered? The answer there is also no. You really only do this when you have a clear upper hand, and that was not yet established.
If those two circumstances are different, then by all means, take a prisoner. But even then, this group has had some bad experiences with prisoners. There are a plethora of issues with taking them, especially those that we will see on a TV show with TV show logic. TV shows don't take prisoners unless they're meant to escape or cause issues. It's just how it goes. We said a couple weeks ago that the writers are going to dictate that these situations will cause danger, and so most of us know that taking a prisoner in this case is a bad idea. It doesn't matter how restrained he is or that basically anyone can watch him, it being TV would necessitate that he cause some sort of problem, whether it's escaping and killing someone, or causing conflict between the green Alexandrians and Rick's group.
So if you're willing to ignore all of the above, then yeah, information could prove to be beneficial to some degree. But personally, I doubt it would be any degree sufficient to warrant risking other lives in the heat of battle. I think that's where it comes down to opinion. How many more people would've been killed if Morgan had stayed with the prisoner? How many lives could potentially be saved provided they got any reasonable intel?
I agree that there are different types of defense for different situations, but they pretty much know the situation, don't they? They know that these people don't have guns, they know that they're nearby, and they know that they have trucks that they can crash into the wall. Knowing all of that is good, but they really can't change their defenses on short notice. This isn't long-term full-scale war, it's a skirmish. For whatever information they've gained, their tactics in this matter are not likely to vary that much. They are going to shoot from the tower and gate, and hole up in the houses. They don't really have many resources currently to do much else, particularly anything specific, unless it was a prolonged war situation.
And further, I'm not sure if the wolves have a plan. It would be nice to know if they did (both as a viewer and as a character), but I think this was it. The plan was to attack and slaughter, perhaps even while the others were away. I don't think they were planning on losing as they had done this type of attack several times before successfully. Maybe they will regroup and attack, but I get the feeling now that the horde may keep them from doing so. It might even prevent them from escaping. I don't think they were counting on that, and I don't think they had contingency plans. Of course, it's unlikely for Carol or the others to know any of that, but it's just one of many reasons that at this point interrogation could be futile.
My own personal opinion is that it would've been better if Carol or someone knocked the prisoner out (being restrained is not enough). Yes, it could lead to the aforementioned prisoner issues, but it's the decision I would gravitate towards. It might be the wrong decision though, and I fully understand Carol's actions. I don't think they were wrong per se, but it's not what I would've chosen.
And I think it's silly to boil the situation down to being a Carol lover if you believe that. I disagree with several things that Carol has done, especially the execution of the sick. I don't think that she can do no wrong, and I think her actions here are purposely ambiguous so as to create debate, and that's something I love about this show. I wish people here (on both sides of the issue) would just discuss more in good faith though rather than being so hostile. Such is the internet I guess. I understand the arguments for getting information, I just think they're perhaps coming from the point of view that we're rational human beings living in a relatively comfortable society. The world they live in, they are forced to make such decisions. However, I think that only a handful of characters would've made the same decision as Carol. Rick, for sure. Probably Abraham and Sasha. Some others may be questionable, but there are certainly more that would not, even just considering Rick's group.
I am curious to see what actually happened with the wolf at the end, whether Morgan killed him or not. Unfortunately, I doubt we're going to see any of that this episode. By the previews, it seems like this one is going to focus solely on those outside in the first episode. We'll probably get a snippet of Alexandria, but probably no Carol or Morgan. I think I heard that the 4th episode was potentially going to focus on some flashbacks for Morgan. That's probably when we're going to get some resolution to that matter. It would make sense if we see what led him down the path to not killing people before whatever decision he's made.
If he indeed didn't kill him and only knocked him out, I'm not entirely opposed to them trying to get some information out of them, but that's purely from a viewer curiosity standpoint. I don't care much for unexplained crazy, and would like to delve more into how such a large group of nutters could exist. I don't think we're going to get that though.