Like most things, manners are subjective.
I've been brought up to always hold doors open for people, be they male or female. I've also been brought up to always say please and thankyou. You'd think those are pretty good manners right? Then I flick a cigarette end out of my car window and I'm seen as evil.
To me, the cigarette end is nothing, especially on a motorway or another high speed road, but to someone else the very idea of dropping anything on the floor is completely abhorrent. The same way that I never break wind in public or near others, simply out of courtesy, yet some people will happily stand there and let one go and carry on the conversation like it was nothing.
I tend to just take everyone as they come as a result. Worry about yourself and let others live how they wish, that way you can be happy that you have upheld your own standards for yourself. I don't think any less of people with different manners to myself simply because everyone is brought up in a different way.