tob doesn't have a problem with little dogs or dogs more his size play is play to him.
i have noticed he will take alot more of a smaller dog if its jumping all over him than the bigger ones ....... he's more ready to grumble at dogs more his own size if they get too carried away.
its body lang jen if indie thinks the dog is scared of her she will take advantage of it most dog's will do that.
like others have said dog's learn the rights and wrongs by mixing with others what ever the breed or size.
tob is still learning that not all dogs play like him and each dog is different as to how they play and what they will take of him.