Yup it's his personal Twitter. No one was contesting his right to post whatever he wants. But as soon as you're trying to address an audience it comes with certain responsibilities. You're free to ignore these of course but then don't be surprised if you get backlash or if new people don't listen.

I'm not really sure why you need to equate being civilized with wearing kid gloves? Is it hard for you to not call people stupid when addressing an audience? Or rather, if you do, does it help? You can call people stupid all you like in private but if you want to educate developers on how to do better I'm not sure why you're so intent on going down this route.

People also often try to make this a generational thing and blame silly emotional millenials but not attacking individuals isn't a brand new concept. And until people stop buying Windows and VS licenses en masse these people have no real reason to worry over their job and thus no real reason to listen to personal insults.