When you talk to him you get asked if you will spare or hunt the beasts in that area, if you spare them you'll get to talk to him, problem is, as soon as you attack anything he'll become hostile again, and you'll have to kill him. I talked to him, got the stuff I wanted, then killed him, saved me some trouble.
Also, your outfit doesn't matter, as long as you arrive through the Darkbeast path he won't attack you.