I think you may be misreading the intent. I've also seen several friendships destroyed because of business disagreements. I take the message as "Don't get into business with friends if you value their friendship."
Replying also to the other comments: Ah thanks, yeah. I've painfully learnt not to lend/give friends money! It cost me a great friendship. But it wasn't deliberate on their part; I guess I read the GP as saying "Expect your friends to fuck you over, and that's ok/your own fault." I am familiar with the risk of business to friendship, but the GP seemed to be going somewhat further, although it seems ambiguous exactly what they're saying.
