Actually not. But I can relate to that. People might just not respond to it too well. They feel offended easily because they take it that they've done something wrong.
Personally, it's a very important quality I search in my friends. In the end, constructive criticism is important to develop yourself. That's why it's good to receive it from time to time.
Though I tend to put things a bit too lightly sometimes, I have no problem if someone gives me a little harsher critisicm. As long as it is constructive or at least I see it as constructive. :P
But I don't think constructive criticism can be too harsh or too light. It's just that: constructive criticism. If it's to light, it's not the real thing anymore - same for the opposite.