This a quick 5-minute edit I put together.  It removes all Nightstalkers from the Animal Friend faction, so they will remain hostile even if you have that perk.  Made for use for people who want a little extra challenge, or those who find it odd that the Animal Friend perk makes Abominations neutral to you.  Covers Nightstalkers in both the vanilla game and Old World Blues.

I recommend making a bashed patch after installing this.