I do not think that it is "wrong" to dominate a submissive with low self esteem. There is a difference between that and exploiting the condition.
I have heard comments by some people that say they would rather dominate a woman (or man what have you) if they have low self esteem. Why this is I can only guess. Maybe it is because they are insecure themselves and wants someone who will not question anything they say or do, accept everything they are told as truth, or have little power to control a person that has a strong sense of self.
Now, I do have a low self esteem, especially when it comes to the way I look and sometimes in my dreams of becoming a published author. Does this mean that I should not be dominated? No. Because TG is very supportive in all my endevours, praises me when he thinks I have done something well, tells me if he has enjoyed the most recent chapter of my novel, and says he likes the way I look.
So to me, it all deopends on the method of domination. If you are going to feed the low self esteem then, in my opinion, you deserve to be shot. But if you are willing to help them see that they are a wonderful and beautiful person in their own right then I see no problems with it.