People ready to fire someone for laughing should not be allowed to work with other human beings at all, in my opinion.
What's going on with this ready to be offended for wind blowing the wrong way culture and the fragile egos?
It's not just about laughing. It's about laughing at someone's work in a derogatory manner. I hope you can tell the difference and understand the extremely negative impact the latter can have on culture.
I disagree. Firing assholes is never bad for culture. On the contrary, it increases morale and makes the workplace better.
Keep in mind that I don't categorize laughing at someone's work as a "simple mistake." Bugs can be simple mistakes. Offensive jokes can be simple mistakes. Laughing at someone's work however is deeply troubling behavior that actively undermines trust and discourages cooperation in the workplace. That's why you have to kill it with fire.
Firing somebody based on your own subjective opinions is toxic for culture.
I've worked on amazing teams with plenty of good natured ribbing and I've worked on great high performing teams where you could say "this code is rubbish, you can do better". I've also worked on teams where saying that would really hurt people's feelings and impact moral.
Put aside your own pre-conceptions and look at how your team responds to an event/situation. That's the only way to build a high performing team.
Sometimes that will mean laughing at someone's code is toxic and needs to be addressed, other times it will be a non-issue and addressing it creates an issue, and other times it can even be a good bonding exercise.
I already specified that this isn't just about laughing, but about laughing at someone's work in a derogatory manner. You seem to be saying "but a laugh can mean other things!" and it's kind of besides the point.
Everyone seems to be taking this too far--parent just mentioned a laugh. It could be anything from a well meaning jab to a mean put-down, and I'm reading it as just something funny for the junior to learn.