This equating of manners to a submissive posture is odd to me. One wonders what is meant by "manners". Saying yes, please, thank you, and holding a door are by no means submissive acts. Table manners, or not acting boarish while dining, is not submissive. Conducting oneself in a respectful, cordial manner is not submissive.
I disagree, I think it is more submissive than doing the opposite. But that's not a bad thing - people who are never submissive don't fit into society. They have terrible manners and drive dangerously, like you point out.
A certain amount of strength is admired, but too much and you're almost unilaterally rejected.