Why is it rude?

Why do I think that so many things in life are rude? During my lunchbreak today I was thinking about why certain things are considered rude in our culture as opposed to the things that are considered rude in other cultures. The middle finger ... why is this a rude finger? My German boss points at everything with his middle finger, and sometimes it makes me giggle inside. The other day a very bothered driver decided that he wanted to drive right up on my butt the whole way to work. I have no idea why he picked me, I didn't cut him off, nor did I give him "the finger." I think he just liked the idea of riding close to a safe driver. Not only was he rude by riding my butt in the car, he also gave "the finger" after I exited! Now, why in the world would he do such a thing and why should I be so insulted? Another thing ... my boss calls me his secretary. Why does that bother me? Why do I think it's rude? Besides the fact that I'm not his secretary (he calls all the girls in the office his secretary regardless of our position), why does it feel so demeaning when he tells all of his bigwig clients that I'm his secretary? Another thing comes to mind ... bodily functions. Whether it be burping, farting, or other odd noises that come from our body, why do I feel like people should excuse themselves after doing what God programmed our bodies to do? For the past week I've been rather sick. It started out slow and then escalated into full-blown nastiness. Since I've been back at work I've used an insane amount of kleenex. Atleast one box per day (we were out one day, so I had to resort to using toilet paper ... I used the entire roll). Now, before the day started I apologized to my co-workers for them being forced to listen to me blow my nose all day. Why did I do this? Is it considered rude for me to not step outside or into the bathroom and blow my nose? Thank you for reading this blog entry and sorry for taking up your time.