My Sadie dislikes most dogs, she tends to ignore them unless they pester her in which case she will see them off. However, when we used to live in London and walk in the local park she did seem to have a particular aversion to black labs. We tended to see quite a lot of them and mostly they seemed to be young and scatty, bouncy dogs who wouldn't leave her alone so she got quite stressed around them. I began to dread seeing them even though I think they are lovely dogs.