Howie made a good point - many want a pat on the back rather than constructive criticism. On a number of different forums related to various interests, I respond most to those who appear to want constructive criticism, as I find this much more interesting.
Speaking of proverbs (in the Bible), there is also a verse in there that says "the wounds of a friend are more faithful than an enemy's kiss."
I studied architecture for 6 years. One thing that was very helpful was being immersed in a culture of constructive criticism and creative work. Criticism is a very positive and helpful thing, we all know that. Often the enemy of our own growth is that part of us that wants to get an A. We want to grow, but we also want peer recognition. We are in the best place to grow and learn when we want someone to help us make something better.
Edward De Bono has some very helpful ideas that relate to this topic. One of his books "parallel thinking" sets forward the of concept of putting forward opinions that might seem to contradict each other, but laying them side by side in parallel. It is in contrast to debate style thinking, where we feel we have to first discredit other ideas in order to promote our own. I've noticed in forums, people often start criticising each other's criticisms! I think there is a place for just laying our own opinion down next to another. Whoever wants to use them can then compare, and use what they prefer. Whichever seems to fit best is taken up, rather than having a debate. This frees everyone up to consider what might have been considered opposing views. Energy that went into defending ones own view, now goes into considering the merits of the other view. I think this is much more creative.
I think part of the problem is that many have not learnt to embrace criticism in a positive way. The other part is that we are human and have conflicting desires.
Going back to uni, I can recall some were dismissive of some of my work. Another might come alongside and say "how can we make this work?"
De Bono wrote another great book on a concept called the 6 thinking hats. The idea is that you think in one way at a time. Black hat = judgement where we evaluate the value or lack of value of something. Yellow hat = how can we make this work? White hat = gathering information. I think when we criticise, we need to switch hats at times, and use the approach that fits. If someone wants a pat on the back, and we honestly like their work, we can do that. If they feel it isn't working, we can sit beside them and work on ideas to make it work. If they are a beginner wanting more encouragement than help, then it's probably more appropriate to overlook major shortcomings, encourage what we see that is good, and pick a few minor things to criticise along with ideas on how to improve.