Well, I'll say that I've treated them as friends. It's kinda hard not to though, since they don't allow you to hurt them yourself.
But anyway, yes I would treat them as friends reguardless. Apparently, even my HM slave Machop (Rock Climb, Strength, Rocksmash, and Cross Chop I think :I) loves me, even though he's still at level 8, the same level I caught him at in Pt. But for the others, since I have cheats for money, I like to give my critters carbos, iron, etc. Bascially, they like it for some reason, though I can never ever find out why D: But anyway, I also try to stay away from those items that would lower friendship.
I'm still creeped out by the messages I get though to let me know they like me. "I wanna nibble yo' neck!" is apparently Tyranitar's way of saying he likes me very very much :'3 and Some of my Pokemon's reactions were just plain wierd in SS. I trained a legityly caught Shiny Bunneary until she evolved into Lopunny, and she gives me wierd messages. She hugs me, she holds on to me, when she gets scared she hugs me, then she blushes a lot....What the heck do you call that? Not bestiality anyway. Humanity? Still creepy. Maybe I should give her something bitter :/
But anyway, I try to treat them all the same. Though walking apparently does help with that. My shiny Monferno, who walks with me almost all the time now in SS, apparently likes me a lot