Apparently, you have never managed any software project for many years. Because if you did, you would realize that people are different, and some far more sensitive to criticism than others. Also a lot depends on the overall culture in your organization. So without any specific context, all those generalizations about what "a wise manager" is supposed to do is UTTER nonsense.
Now if we speak about the Linux kernel, the fact is the success of the Linux kernel is largely due to Linus ability to keep many talented people involved, and he works with same people for many years. So whatever words he chooses to express himself, it does not seem to affect his working relationship with those people. Also I do not remember that he has ever criticized newbies, who are still learning, or anyone like that. Practically, all his harsh words were directed at his lieutenants, who were entrusted to keep the source code to a certain standard, but failed to do so.
Finally, I will never trust you (or anyone else) just because you are willing to work on some stuff. I can trust you only if I know that you can deliver the result that meets certain requirements. I had a developer who tried to be nice and willing to work on almost anything, but his code was nearly always crappy, so giving him nearly any task (aside the most trivial stuff) was completely useless. So we had to part with him. So the question is not what you are willing to do, but what you can deliver in practical terms.