Shit! I accidentally deleted my last post while trying to modify it!
But yes. Without a rigid definition of "emotional maturity" and scientific testing we're both just blowing a bunch of hot air. Come to think of it, we'd also need a rigorous definition of "bad". I think there's definitely some minimum cutoff for required emotional maturity below which things do indeed get bad, but I'd wager the cutoff is lower than where you think it is, instead being in the range of violent posessiveness and actually disordered personalities.
But until I can find anything solid for or against, I will concede the argument.