You have to realize that all of those external appearances mean very little.If things degenerate into a physical confrontation, you will not be fighting his weird hair, the ink spots on his body, or his raggedy looking clothes; you will be fighting a human being (I use the term loosely in this case).This is something that every true warrior needs to think about.
Many times yelling and threatening signify someone who is not capable of following through with his threats, but is merely trying to bluff and intimidate you into getting his way.
It is the silent predator, who acts with no warning that is the most dangerous.
Protecting yourself from being intimidated in high-stress situations involves training for such a situation in advance.
This is one of the purposes of realistic scenario training.
Some sense it as a strong self-confidence and other can sense it as simply someone who is standoffish or dangerous, but I can assure you that people can sense something different about true warriors.