At least with Vincent's quest you didn't know it's going to happen.What's even the point of raising 4 people's Strength to 40+ if they're just going to be straight-up murdered. That's pretty ass.
I feel the same about the four blondes. The mechanics there, IMHO, should be the same as in selling a slave at the market.
Getting the blondes to be your companions, and everything that involves, seems like a time consuming hassle to me, because I knew I'm going to lose them from the start.
Plus it left me with an ugly feeling, which is perhaps the Dev's intent. :-/
Working to get a slave all the way to companion, with the full knowledge you're about to betray the girl felt nasty.
Maybe the Dev wants the MC to be portrayed as an unfeeling a-hole.
It is a rape/slave management game after all...