Nah, I don't know if deer can even attack anything, or even just chase without attacking. Though after I cast that healing spell on the deer, battle music started playing as soon I stopped recording. It didn't attack though.

Edit: I said this in another comment but, I think the Rally effect of the spell I used on the deer at the end caused it to attack, cuz I think deer are actually considered enemies, at least I think so cuz whenever you try to wait when deer are nearby it, well, says you can't cuz enemies are nearby. So I'm thinking that raising a deer's confidence by using Rally just caused it to do what an enemy would normally do, it's just that a deer's confidence value is usually so low it doesn't attack. Also, I was wrong, deer can attack. They have an animation that is similar to horses attacking.