My dog has lead aggression. Well, it's excitement, he loves other dogs but he gets so worked up and happy when he sees another dog while he is on lead that he can easily translate to aggression.
He was well socialised as a pup (he wasnt my first dog and my Nana was a breeder so it's not like I am completely clueless) and as a young dog. He did come from the SPCA at 10 weeks old.
Anyway, I always make my vet appointments for the last one of the day with him so we don't have to worry about freaking out another client when he starts acting like a lunatic. An, we dont go and wait in the clinic either. We wait in the car until the previous person has left.
(lol having a chuckle about this post in relation to the "watch dog" one, I just paint my dogs and myself with the most beautiful brushes dont i)