dachshund is mean towards other people

Question
My mini dachshund is going on 4 years old next month.  My only concern with him is that he barks and growls at strangers, and will chase after them and try to bite them if they are scared.  If the stranger is a dog person and puts their hand out in a friendly way, he will stop barking.  But if they are scared of the dog, he will try to bite them if i don't stop him.  I understand it is his nature to be protective of me and may never be friendly towards strangers, but i don't think this behavior is right (please let me know).  If i take him for a walk he will try to run up to strangers and i say no and stop the leash but he will growl at them from far away.  can i train him ignore strangers?  on rare occasion he will walk right past them

a little background info - he is the first dog i have owned and when i got him i was living with my ex girlfriend who had a dog that was not friendly and barked at strangers and tried to bite their ankles. i should have walked them separately, but i did not know better. also my girlfriend liked it when they barked at people and tried to bite them cuz she saw it as protective.  
- my dog is friendly towards other dogs, so wont bark at strangers if they have a dog
- my dog latches on towards one person.  it used to be my ex gf but now it is me.  when she would leave the house he would cry even though i was there when we lived together. now i am the one he latches on to. when i visit my parents, he barks and runs up to them when they enter the house, and then stops immediately after he runs up to them.  so i dont think his behavior is too bad, it all depends on the persons reaction how he will react, but it will be bad if they are scared. the other day a little kid wanted to pet him but i said no because i dont want to take any chances. should i just accept my dogs behavior, or can it somehow be changed and i won't have to worry about him biting strangers?  if nothing is wrong, please let me know. my vet shrugged off my concerns of his aggressiveness telling me he is just being protective and i am number one, but i have my doubts.
- he is house trained

THANK YOU!

Answer
Hi Joe

The dogs needs training STAT and unfortunately, so do you.

By the sounds of things you are sending the dog mixed messages about what's acceptable and when.  He's appears to be a defensive dog and one that needs focus and structure.

There is never any excuse for biting or barking, and small dogs are the worse offenders.

Check with training schools in your area and get him enrolled, the alternative is a) he is going to meet a bigger dog who isn't afraid to teach him a lesson or b) you are going to meet a bigger person who isn't afraid to sue.

Good luck