If "god" didn't want animals to get high he wouldn't of made them with Cannabinoid receptors. I mean... that IS why we feel the effects of THC... is it not?
Yeah their brains are small but how mutch THC is absorbed into your lungs before you exhale... if you force an animal to get high, that's obviously bad. If a dog loves to eat your weed and get stoned, that's his deal. If a pet comes to you when you smoke to be around its aromatic effects... that's his deal. My little dog runs when I reach for a bong, so I never get her high... BUT she will sit in the room after we smoke and fall asleep in the hot boxed room every time and get herself high.
Other dogs put their nose right to your mouth and try and get some smoke hahaha (seen it). But you have to introduce it to them somehow, if they don't like it they don't, if they do, they'll know what's up and hang around lol.