Cecile

I have a 6 month old doberman named Cooper. He is a wonderful dog until he gets around strange men or larger women inside and outside of the home. He was adopted from a very small breeder who maintained only 5 dogs of her own and was very passionate about socialization and both of his parents very well rounded. So i'm thinking that i've made an error somewhere with socialization. He will usually smell a person then suddenly decide he does not like them, back off and bark incesantly. I've taken to carrying a can of pennies to curb the barking (which does work), but i'm afraid of making him too timid which is inappropriate and not the standard of his breed. We have no problems withj children and he is very affectionate and learns easily. Any suggestions?