There's an art to criticism, just like there is an art to conversation, and flow training, and 2 main reasons to participate. (There may be more, please let me know)
One is to interact, understand, learn something new perhaps, or make the other look to improve their work. It is entered into with an open mind without preconceptions about the outcome (I know this part is hard, but say as few preconceptions as possible) and is hopefully a learning experience for both parties to increase excellence on both sides.
The other is purely to put something down, close it off, with a mind already made up, seeing evidence that only supports a presupposed theory, and none that negates it.
The first is about 'not knowing yet', the second is about taking comfort in the sound of your own voice. The first about trying to understand what you don't know, or to try to change the mind of the other, the second does not care about effecting any change, just about stopping the other. The first is interactive and involves 2 people, the second needs no second viewpoint.
As an aside, one of my pet peeves is having a so called conversation with someone that does not believe the listener is a participant too. My rule is that if I could replace myself with anybody else, or a cardboard cut out with no effect on the words being said, then it's not worth wasting my time with. Similarly in flow training. Flow training is about LEARNING. It is a very different animal than fighting where the object is to win.
When winning is the objective, then screw the 'other' - there's be no back and forth, or generous creations of openings, pauses, politeness or trying to understand ... there would be ranting with no chance of a counter, no care about learning something new or helping the 'enemy' improve their game.
So, conversation, criticism and training, and 2 ways to go about it - the learners who play/flow/converse, and the fighters who want to consolidate their positions and only see enemies, not allies.
Personally I don't think I'm done with learning yet, I know there's alot I don't know, so am willing to try to understand opposite views. I suspect there are many others who are the same as me in this respect, but there are also plenty of folks 'fighting' to shore up their positions in any way necessary, who have no intention of letting other thoughts and ideas threaten them. They see all interaction as combat, with winning as the objective. Not sure yet how to talk with these folks .... not sure if it's possible, or desirable, but occasionally I've found it interesting to be 'the enemy', and very useful for understanding the difference between fighting and playing, even though it is only with words.