I have a small dog. It's very clever and well trained, but it's still an aggresive asshole.
The issue is that it's difficult to socialize small dogs to begin with, when all the other puppies are quadruple the size.
We try it sometimes, when she seems interested in other dogs, but it always ends up the same with her getting scared and aggressive for no particular reason.
It might be easier if I had had an older dog to begin with or something.
She's not aggressive against humans at all though.