This happens with Sunny all the time. I'll walk by someones garden and I can't see inside, because there is a 6ft fense, and a dark'll just start barking his head off. Sunny doesn't care at all.

He's just like, "Where are we going next?".
When the next door neighbours son comes over with his dog, and its in the garden barking its head off. He'll bark, growl, show his teeth and try to get at Sunny. All Sunny does is just sniff him (there's fence panels in the way) or just ignore him completely.