> Why so smug?
Yeah, the alpha geek passive-aggression is a tiresome aspect of our industry. Usually that smug self-assuredness is worn down by harsh experience, but heaven help you if you meet a 40 year old alpha geek who has not yet learned that they too can be wrong. (I work with one, and he makes some shocking mistakes but cannot admit it, so when he launches at you with a holier-than-thou attitude, scorn and contempt are all that arise).
> What happened to good grace and manners
Exactly. When you're totally right and someone's totally wrong, if you want to effect actual change (assuming that doing so requires their coöperation), grace is precisely what's required. You can have all the technical correctness in the world behind you, but the moment you put someone's back up with your poor attitude, the chance of them rationally engaging with your argument drops dramatically.
I've had this argument before with some people on Reddit, and I received the retort "But who cares if I was rude, _they_ were wrong, I was telling them how to fix it!" ad perpetuam from one particular person who was astounded that no-one took his advice.