Why are some people in a permanent state of aggression?

You are right. Most of the time it is what we eat that has an influence on our moods. One needs to test the blood where one will find electrolytes imbalance which leads to mood swings and other psychiatric disorders. There could be other factors as well but no one gives a serious thought to this aspect. If drinking in excess can result in changed behaviour why not eating certian foods as well!!

what u eat what u watch,what u listen to the information that u input within your system as alot to do with the lifestyle we have adapted to,and its in some peoples nature to be aggressive and they like it that way,its all apart of the cycle of life we live and wee learn

I think it's probably a bit of everything that you say, maybe different things for different people. I have noticed that recently people seem far less able to control their anger or to express it appropriately/constructively. Also I think there is a body of people who bottle their anger about small things up, store it, then it spills over in one huge mass as an enormous rage, whereas if they'd let it out in bits (and constructively) at the appropriate targets, people like your husband then wouldn't have to be the butt of accumulated anger that 90% of which was probably intended elsewhere.

Seems as if the woman had ego problem and did not like to be corrected for wrong parking.

I pick the shoes to be too tight! Why else would she hurry off out of the car and not park where she is supposed to be? She kept looking at her shoes/feet that's why she didn't notice the lamp post. Also, why else would she be stomping her feet? It is to make her feet numb and not feel the tightness of the shoes.

I think people act angry all the time because they're just so use to negativity and always responding in that manner. They don't know that with just a change of thought, they can be happier and not so confrontational with others. I also believe that it's also what they go through or went through in life, as well as biological factors. Sometimes, people just go through a lot of terrible events in their lives and they don't really know how to respond, so they respond in the best way they can; with aggression. Sometimes people are also just naturally cranky all the time, maybe because of their parents passing down certain genes. She could just have been very short tempered or maybe something terrible that got her angry at the world happened to her on the way to her friend's house. I mean, it really could be anything to explain why she seems angry all the time. For people in general, I do think there are a lot of factors to consider because there are many sources of aggression for different people, so it is probably true that all the thing that you listed out could each in itself, be a reason why people seem so angry and confrontational all the time.