Basic Universal Etiquette?

I used to believe that there must be some basic universal etiquette common to all human beings regardless of the societies into which they happen to have been born. But this belief has been crumbling down slowly but steadily as I see enough people here in Israel who do not seem to share this etiquette. When I see those behaviors that must be considered uncultured in many other societies I know, I cannot help wondering what kind of education these people here have received from their parents and school teachers and whether this is a norm rather than an exception in native Israeli culture.

There are a number of social settings in which I believe you should not eat foods or chew gum. Unfortunately, I have to repeat the same request to stop doing so every year to the same group of people in a certain social setting that affects me personally. What surprises and bothers me every time anew is their common reaction to my request: they react as if they did not understand what was wrong with their behaviors. This lack of what I consider basic etiquette is found among both secular and religious people here. To be worse, it is not uncommon even among otherwise respectable people. I almost had a heart attack this week when I saw such a person daring to chew gum in a rather formal social setting from the beginning until the end!

Another example is that unfortunately, there seem to be quite a few people who do not know how to distinguish between what is public from what is private, doing what for me is not permissible in public. Lack of this etiquette manifests itself in various forms, including speaking very loudly (or screaming) in public, discarding garbage in public space (not in garbage cans), knitting a yarmulke during lectures, writing personal notes in books in public libraries, not returning books after reading to the original location in public libraries, not erasing your notes on the blackboard after teaching, not flushing water in public toilets after using, etc. These are for me signs of egocentric childishness.

I have given up every hope of understanding these people and explaining to them why these behaviors of theirs are not acceptable. Instead, I am trying to pay no attention to them and their behaviors as long as they do not affect me personally, and make sure to have enough physical distance from them. I would only like to hope that they do not consitute the majority here, though there are many of them in absolute terms.