> If yelling/lecturing/screaming at an employee gets the point across and prevents them from being fired, is it justified?

Good question! I'm going to say no (except for lecturing, which I'd say is different than the others) for a few reasons.

First I'm going to claim if your actually being clear this situation doesn't exist. Being clear means making it clear how serious the issue is and spelling out the consequences if the behavior doesn't change. Imagine Fred has been filing his TPS reports late every week, and in our industry late TPS reports are a serious liability. I've had multiple conversations, starting with "Hey Fred, your TPS reports were late this week. It's actually really important that those are filed on time." To more serious conversations where I've invited him into my office given him a chance to explain what the situation is, and made it clear why it's so important and that this must be done. And his TPS reports were late this week. Fred's on his last chance.

The way to deal with this now is to make it clear, this is it. "Fred, we've had multiple conversations about your TPS reports. When I asked you why they were always late you said you kept getting busy during the week and it was hard to get them done. I made it clear they were higher priority than your other work because not having them puts us at risk for X, and told you to prioritize them, and come to me if you need something taken of your plate to get them done. You haven't done that. This is a serious situation Fred. I'm going to be paying attention to make sure you file on time from here on out. If your reports are late again, you will be fired. Do you understand?". Then listen to Fred's response and drive home the point if necessary that he will lose his job if this doesn't change.

On the other hand I could drag him into my office (or just do it at his cube) and scream something like "Fred what is wrong with you?! I need your TPS reports! How hard is that? If you do it again your fired!" Really imagine someone screaming it for a moment. See how unhinged they look? In the first example it's clear to Fred that he's going to be fired if it happens again precisely because I'm in control and calm (not calm does not mean not being firm). In the second Fred's not sure if that firing threat is real or if I've just lost my temper.

But let's say for a moment Fred's not normal and really does just respond better to screaming than clear communication. You need to fire Fred. You can't have someone on your staff who you have to scream at every time you need to get a point across, and if he's like this with you, he's going to be difficult for others to communicate with too. I assure you, you can find someone just as good as Fred who isn't this difficult to talk to.

But Fred is weird in that he responds best to screaming AND he's a savant at his job? You really don't think you can find someone who can do the job as well? I doubt it, but even accepting that as true... Fred's gotta go. Up till now, we've just focused on the impacts to Fred, but the rest of your employees will be paying attention too. They'll see how Fred's treated and that's what they'll expect from you. If your screaming at Fred, they're going to be constantly afraid that if they make a mistake they'll get the same treatment. This may result for example in them attempting to cover up a mistake instead of working with you to resolve it. This same effect is why it's important to manage people out compassionately. You might think that it's fine to tell Fred to "pack up his shit and get out, he's done", or maybe just let him discover his key-card doesn't work one day, after all, Fred's going right? What's the point in being nice about it? But your other employees will be paying attention and they probably won't see the line of disciplinary discussions or issues that you haven't advertised leading up to this action, so it's important to handle the situation with as much grace as possible for their sake if not for Fred's.

If anyone is still reading this I'll also note I separated out lecturing. Depending on how you choose to define it, lecturing may be appropriate. By that I mean explaining why it is so vital in our industry it's so vital that TPS reports get done on time, so that the employee understands that this isn't an arbitrary requirement. As much as possible you should try to avoid making it a lecture where you talk and their eyes glaze over and keep it an interactive conversation, but one could easily imagine an employee then reporting "I got lectured on the importance of TPS reports", and that interpretation may be unavoidable.