It's a trait, so there is no real reason why we shouldn't be able to get it.
And it can be very useful. For starters, anyone who tries to lynch me this game will have to consider very carefully if that idea is good for his health.
Also, I -will- sub back in and go after any hunter or leader villager who tries to kill me because of some "goodies can't be brutal" nonsense, thanks.
Ah, reminds me of the days when I randomly shot you, you subbed in and I immediately set my brutal on you. It's a shame I was hunted in that game...