I've also become very aware of the fact that we really have to be careful with these things. When we are little we are taught to be very affectionate. Here is an example. It would be cute if the daughter went to hug him or even kiss him on the cheek goodbye. The truth is that as we grow older, simple things like asking a boy in our class over for a play-date become quite complicated.
Some people are naturally affectionate.
Some guys hold doors for all women, not just those who they find attractive. While it's nice polite gesture, a problem arises when such gestures are misinterpreted. This is not to say that guys shouldn't hold doors open for women who they don't find attractive. The problems caused by flirting are not ones that can be solved, but they can be dealt with. Let's say there's someone you're interested in who touches your arm or your hair while you talk.