Agreed. I hold the door open for anyone and many people hold a door open for me. I always say "thank you" and almost always receive a "thank you." I've heard stories about supposedly radical feminists getting angry about it (like the tweet referenced in the OP) but I sometimes wonder if that's urban legend intended to make feminists look bad because I've never experienced it or witnessed it. Sure there are people who aren't polite and don't say "thank you" or don't seem to care that you've done it, but I've never experienced the angry "I don't need a man to hold a door open for me" comment, or anything similar.