If you were fired in front of all of your coworkers, what would you do about that?
Professionalism is important, and that extends to the higher-ups too. Too often, bosses feel like they can get away with something because they're the boss. But just because you're in charge doesn't mean that you're automatically in the right and get to exert absolute power over everyone else. This isn't how most people like to be treated, no matter who they are. The employee in this story didn't deserve to be called out in front of the entire group. This is no way to treat people, even when you're firing them. Nobody wants to feel like they're being made an example of, even if they are.
Have you ever had a job with a toxic environment? Luckily, I haven't experienced that... yet. But I've heard tell of so many toxic places of work that just don't seem to give their employees a break on anything. They have a culture of toxicity, and it's rotten to the core. Or maybe it's just one person who makes their own insecurities into everyone else's problem. Whatever it is, it makes you dread showing up to work. This is no way to live. That's what this workplace clearly was, evidenced by an incident that happened in the workplace group chat. Group chats can be tricky things. They're places where things get decided, and stuff goes down. But there is plenty of drama that can pervade a group chat. They're not always the friendliest places, especially in a toxic workplace. There is a lot that can go wrong in a group chat, and this employee figured that out posthaste. They couldn't expect that their ultimate termination would be aired out for the whole world to see.