Yes, he is very slytherin though. I think most people imagine the more insane or evil slytherins when they think of slytherin, but Slughorn is definitely the one who seems slytheriny (if that is a word) to me. He manipulates and charms, gets in good graces. That's how I imagine them, but they aren't presented like that in the books often. He really is a good example of a slytherin, who wasn't a death eater.