A child who cannot take no for an answer is not sensitive; he's defiant. He's defying you because he has learned that he can get away with it. It sounds like there are no firm boundaries set and that he is unable to restrain his impulses. When we do not discipline a child who's acting out, we are doing him (and ourselves) a disservice, both in the short-term and in the long-term.
In the short-term, we are sacrificing peace and harmony, and in the long-term because a child who is not disciplined properly cannot possibly learn to self-discipline. And without self-discipline, no-one can achieve anything of worth in his or her life.
Depending of the age of the child in question, and assuming we're not talking about the 'terrible twos', it is imperative that you step up as a parent and take control of the situation.
I've written a hub on the 8 lessons we must teach our children. Here's the link:
I wish you well on your parenting journey.