Agreed... but that keys on friend... thsts where the social interaction rules come into play as they emphasize the traits and specifics of the who and what.I wouldn't allow a persuasion check to convince someone to attack another current friend. Would you attack a friend if another one asked you to really nicely?
If they were close, maybe like I said try and stop the fighting, not kill the other.
But if they did not like each other...
This also comes down a bit to robust GMing. In my dwarf tiefling gang encounter, I had well before then shown a division in the hirelings and the tiefling exploited those prior references specifically in her statements.
So in the case of two cyclops, somewhat mythical known for their internal disagreeability, whether the GM had planted seeds of them being brothers, allies, liked, hated etc each other... goes a long way for enabling or disabling this choice of tactics.