The question here is why some girls will haul off and kick a guy in the valuables for holding the door open. I'm glad to say that those instances seem to be decreasing over time, but it still happens sometimes. I think I know why, and it's the classic source of
trouble between the sexes (hell, between
humans...)
Miscommunication.
There are two very different reasons to open a door for someone.
1) If they are very weak, or old, or burdened, or sick, or tired, or drunk, or whatever. If that person seems physically incapable of opening the door, it's considered kind and courteous to hold it open. (Please note that even though I am an objectivist (little 'o'), and also reject the social contract, I still do the above every time the opportunity arises; I see no contradiction there.) This his how some women always see it, as if the guy thinks she is weak or incapable of opening a bloody door. I can see how that would be offensive, I really can. I also think that that's not how it's usually meant.
2) This is a bit complex, but it's how I understand my desire to hold doors open for my gf. I respect her. I am constantly amazed by her, by her talents, by her capabilities, by her wit and strength. I am bigger and stronger than she is (though not grossly so), yet I still realize that she is perfectly capable of opening that door just as well as I. And that is exactly why I want to open it for her.
See, I know she can open that door. I know she can pay that bill. And for that reason I take pleasure in doing it. It is my pleasure, and my honor to do so. If I really felt that she was incapable of opening the door, it would be an entirely different feeling, more of generosity.
There are some guys out there who, on some level, believe that the girl in some way cannot open the door. That breeds a condescending view, and they guy might eventually say, "Hey, you can open your own damned door." That's what a lot of girls think is always going on, that the guy is looking down on her. That's not always the case. When I do it, it's out of admiration, respect, and love. Quite the opposite of being condescending, it's a token of my respect.