We have a cattle dog mix but we dont tend to take him out in public much. He can be aggressive and he's also a big barker. J did take him through obedience class through petsmart and I dont think anything happened there. Sounds like a rather silly generalization. All dogs have such different backgrounds and upbringings and experiences, I just dont think it'd be possible to give a blanket statement like that.

But about the breeds sticking to their own kind... I will vouch for that. When we take Eli up to the dog park, there's always multiple boxers and they always tend to stay together and play with their own kind. Labs seem to do it too there. I think it has some to do with theyre energy levels. The boxers are all younger and tend to run all over like crazies so it'd make sense for them to be drawn towards each other. =)