And, this is why we don't have follower rules in the game anymore.
I much prefer player facing rules to be actually player facing. Then again, if I'm worried about my players suddenly becoming mass murderers for no reason, maybe it would be more of a concern. Since I don't play with dicks, it's not a concern.
I think the concerns are not so much mass murderers but rather
mature roleplaying
We have a player at our table who's strong suit is not
role playing, in my estimation.
In an instance where the players were controlling multiple characters, he found himself in charge of 3 clerics of different faiths. They were his characters so he was familiar with them, they were not thrust on him.
There was a rather significant decision to be made and there was much dialogue and a social exchange occuring between the PCs and NPCs. Another player at the table called him out for playing the clerics all the same way despite their obvious differences (sex, race, culture, background, creed...etc)
This is not the first time this player has created wtf moments at the table both with DM (myself) and the players. I've spoken about this before, but this player is the reason I will not use Plot Points (DMG 2014) at my table, after a rather disastrous use.
We cannot trust him to use that device to build a better or interesting story.
Now I have only one such player at my table. Imagine someone has 2 or more players like that.
I'm lucky in that if I had to use the Bastion Rules I could allow the players to control the hirelings leave it to the players with maturity to run things and outvote his power-gamist tendencies, but if I were running a table with more such players, I would never leave NPCs in their hands.