D&D 5E Is Charm Monster too good?

[Maxperson]

I mean a random human might not have those same social ties to their friends as others. That said it does seem a bit over the top for any creature to attack it's old friend to protect it's brand new one. It's possible and plausible but seems extremely unlikely given any random creature.

My basic take is that a creature doesn't attack it's friends and that it would take convincing the NPC that it's old friend was an enemy before it attacked him.

What would it take to convince you that your friend(pick any friend) not only is an enemy, but one that is so dangerous that he needs to be immediately attacked and killed?