Milan dogs in this world were born to explore. Keeping this in mind pulling and chasing birds, dogs, etc is very normal. A dog nose is 100 times more sensitive than humans and a breed like Labrador will sniff everything he comes across.
Having said that, you can certaining train him not to pull while on leash. The training is based on the principle that your dog has several choices- he can pull, sniff around, mouth dirt, bark unncessarily, try to chase other animals and all other negative behaviours. However only good behaviour- walking along gently-will yield possitive result. The good behaviour will yield good result which you can offer by offering him favourite treat. This way your dog can distinguish what's good for him and what's bad for him. It's very important for you to enfore the Principle- Good behaviours good results.
You can apply this principle whether it's leash training or any other training.
Implied is an answeer of your question whether physical punishment is right or not. Bad behaviour should be ignored. If you beat your dog, that will be unfruitful because your puppy would never know why he's being beaten. He will be confused and won't understand anything. Out of confusion, your puppy may bark at you, may bite but won't understand your command.