Odie too is like that. When I take him to the dog park he'll play well with some breeds and others, well let's just say that he gets rather ornery with them. He'll bark at them growl and for no reason. He loves shiatzus but jrt.. forget it!! He just goes nuts. His bestest friend is a shnoodle he loves her to pieces. Probably because she protected him when he was a baby.
She still watches for him and if there is a dog in the park that is bullying Odie she'll go after them and make sure that Odie is ok. It is really cute to watch.