The problem is, everyone has their own set of limitations. whether it's lack of skill, lack of money, a physical limitation, etc. How are we supposed to enforce some sort of "acceptable" level of criticism that's different for everyone depending on their own personal situation? The answer, of course, is that's impossible.
Like I said, if you can't handle criticism from the public, don't post your models for the public to see. I don't say that to be mean, I say it because it's just the way it is. If all we allow here is pats on the back and comments like "awesome build," then the whole point and meaning of a public forum is lost.