The ad hominem attacks on the ad critics: who is allowed an opinion?

I've noticed an uptick of a particular style of comments recently. There's those who will jump to "you are bitter / you are a hater" retort. Then there's the "what work have you done?" resumé-demanding retort. Then there's the scanner, s/he who reads the headline and will post replies on what they assume the article says, rather than finish reading it. The scanner might have been born from too much twitter.
When I was a young ad-pup at school, I remember how I had created a bad poster. It was terrible, and John Gillard ripped it apart (quite literally, screw that it had taken me hours to draw this work pre-computer print out days), and snapped at me: "Will you be standing at every bus stop explaining this ad to every punter that reads it?" No, of course not. "Then make it impossible to misunderstand." and off he went in a huff while I, fuming and beet red, realized that he was absolutely right. I shan't defend my work to strangers, I shall make it better. To learn how to take criticism gracefully was part of my ad education. Paul Arden told us all to not to seek praise, but to seek criticism. Only then will we improve.
I'm wondering if this new generation less prone to be able to give, and take, criticism? And who exactly, is allowed to critique ads? The Ad hominem and ad feminam attack comments here seem to often come from a place of personal injury. Examples, The Alpha1 stunt I thought was lame got this comment from the agency that made the ad, the Depressed copywriter just called me "bitter" for snarking, I've even had my life threatened more than once, and I've lost count at how many times I've been called a bitch.
But sure sure, I'm small potatoes. I'm nobody. I'm not allowed to critique advertising until you've all inspected my Lions first. Right.
Does this happen to everyone, I wonder? Lets ask Luke Sullivan He is an undeniable USA bonafida ad-giant Lucky Luke, he has his own blog, his best selling ad book Hey Whipple has been released in several editions, and he has written a self biographical book on his childhood called "Thirty Rooms to Hide In : Insanity, Addiction, and Rock 'n' Roll in the Shadow of the Mayo Clinic