Yes i agree, i have had GSD in the past and i would never ever let her out with either of my sons. They are such a powerfull dog and if another dog came to attack you can not expect it to ask the dog to wait until the little lad has gone in. They will fight.
I have a cavalier and i hate it when big dogs come over uninvited as i have worked in kennels and you can never be sure that the dog is not going to dislike the one it meets, it can be the simplest thing such as smell or the way it looks.
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Grandma to Jinja Dog, Mum to Tilly the Cavalier, Tattycat, Moomy, Choo, Sonic, Niven Mc Twisp and Lawna the rabbits and 1 guinea,17 budgies, 4 Cockatiels, 8 Goldfish.