Just be careful not to make companions overly aggressive when hit. Accidents happen, especially with missile weapons, but there have also been accidents where you spam "attack again" and you missed that the target was dead and a dog (or companion) moved to that tile, and you don't want your robber hunting posse to devolve into a free for all when everyone is fighting against everyone else.
Yes, accidents can happen, and I believe the placid companion reaction to player character attacks is originally in place for that very reason. And it wouldn't need a chance, if there wasn't a raise of abusive playstyles when the exploits are pointed out.
To define overly aggressive here, is a good question, and an interesting AI dilemma.
If the companion gets one accidental blow of a sword or an arrow in their back during your adventures, they probably should take it as an accident. But what if that happens frequently...
Companion: "You shot me in the back!"
PC: "Oh, sorry, I'm just not very skilled archer. I was shooting at that squirrel, you see."
Companion: "This happens every time we are hunting squirrels. This is the sixth time now."
PC: "It was an accident. Sorry."
-- time passes ---
Companion: "You shot me again. This was 27th time."
PC: "It was an accident. There's a squirrel over there you see."
And maybe on the 28th time the player character succeeds with this masterplan of shooting the companion dead and robbing him during the hunt.
Well, we don't want to invest too much time to address this, as the murderous characters will keep on doing it the way or another, but one way to go about it would be to add counter of tolerable accidents. But still, if the first "accident" is tolerated, and the character actually plans to take the companion down with carefully planned attack, they still have a second attempt without consequences - and the exploit remains.