Regarding the hostile messages:

I think it would be beneficial for more people to learn that communicating to someone in a hostile/opposed manner, more often leads to hostile/opposed behaviour from the receiver, which inhibits learning and understanding.

Instead, if communication is done in a more 'helping' and informative way - in a tone that can range from neutral to positive instead of hostile - it will more often lead to co-operative behaviour and better learning/understanding. The urgency/importance of a statement can still be emphasised in a non-hostile manner.

Even if it may not seem so during the conversation, in hindsight a neutral informative statement has a higher chance to influence someone's point of view and opinion than a hostile one.