3 1/2 yr old aggressive behavior

My 3 1/2 yr old son who is an only child, is very aggressive when he does not get his way.  He will hit and kick when he is restricted from doing something he wants.  We put him in time outs for this behavior.  We tell him that hitting and kicking is not the way to treat people and it will not result in getting what he wants.  Also, when playing with other children, he can become mean by pulling girls' ponytails or pushing boys down.  When asked why he does this, it is "because I don't like him\her" or "he won't play with me".  My husband and I are very calm people; we do not exhibit this type of behavior at home nor do we allow our son to watch aggressive cartoons or movies.  He seems to be "naturally aggressive".  He is also very strong for his age.  Since birth, he has measured in the 90% in height and around 75% in weight.  I do not want to end up with a very large, very strong, very aggressive child.  How can I stop this behavior?