I don't think he's assuming anything, he's just stating that "since it's a rare type he won't harm it" because of the whole "i could sell it for a high price." idea.
Now, now, don't get so angry.And where are the little ones!?Hurry up and let me out!I won't do you any harm.Why would you do such a thing...!Mister Human...!Oh, you're awake?you're a rare-type!After all...