The quotes are all from different Halloween movies, in no particular order.
[Referring to a partially eaten dog.]
Brackett: A man wouldn't do that.
Dr. Loomis: This is not a man.
[After Michael falls off the balcony]
Laurie: Was that the bogeyman?
Dr. Loomis: As a matter of fact... it was!

Dr. Sam Loomis: I met him, fifteen years ago. I was told there was nothing left. No reason, no conscience, no understanding; even the most rudimentary sense of life or death, good or evil, right or wrong. I met this six-year-old child, with this blind, pale, emotionless face and, the blackest eyes... the DEVIL'S eyes! I spent eight years trying to reach him, and then another seven trying to keep him locked up for I realized what was living behind that boy's eyes was purely and simply... EVIL!
Marion Chambers: Don't you think it would be better if you referred to "it" as "him"?
Dr. Sam Loomis: If you say so.
Marion Chambers: Your compassion's overwhelming, doctor.
[After Michael disappears]
Man in pajamas: What's going on out here?
Sam Loomis: Call the police! Tell the sheriff I shot him!
Man in pajamas: Who?
Sam Loomis: Tell him, he's still on the loose!
Man in pajamas: Is this some kind of joke? I've been trick-or-treated to death tonight.
Sam Loomis: [looks at the blood on his hand] You don't know what DEATH is!
Dr. Samuel Loomis: You talk about him as if he were a human being. That part of him died years ago.
[Talking into the woods]
Dr. Sam Loomis: Michael? It will destroy you too, one day, Michael! This rage which drives you. You think if you kill them all it will go away? It won't! You have to fight it, in the place where it's strongest! WHERE IT ALL BEGAN! If you want to get rid of this rage, Michael, go home, GO HOME! Go to your house! I shall be there waiting for you! You will find HER, waiting for you!

Dr. Sam Loomis: I prayed that he would burn in hell. But in my heart, I knew that hell would not have him.
Doctor Sam Loomis: I knew what he was, but I didn't know why.