I'm completely shocked sometimes with owners. There's an owner at Hunters agility classes that's like this. Since we're still learning most of the dogs are still on leash except for tunnels etc. Well this terrier X (~20lbs) in the other class, comes charging up from the other side of the field (he'd gotten away from his owner). Luckily we saw him coming since he was headed full speed for the 2 lb pom in our class. The owner just laughed and said he just wanted to play (a 20lb terrier even playing would probably kill that pom). Non of us were very happy but ok it can happen, but this happend twice more during the class (he always went for the same pom), then again the next class but this time went charging and jumping on the bigger dogs, Hunter included. We were lucky in that none of the large dogs in our group are aggressive. We were happy when next session that class had been moved to a different time slot. There was never an apology from the owner nor any discipline for the dog which is what really ticked us all off.