It doesn't come across as particularly rude given what the offense here is. Someone blamed other projects for their mistake after getting called out. That deserves harsh criticism.

I think you are talking about American ideals. Not ideals in the English speaking world. Nothing here is remotely toxic by British standards. Swearing isn't a big deal here, people regularly call each other swear words as a sign of affection. If someone does something stupid you can say they are acting like an idiot and hopefully they will listen. If you didn't they might not think you are serious.