There are a couple of ways of looking at the locked doors. One is that congress has a place to conduct business without interference. The other is that congress is supposedly in session in a public building paid for and maintained by the taxpayer, and congress is supposedly there representing us and is supposedly answerable to us. I'd maintain that if they were doing the second part people wouldn't have been barging in to remind them why they are there in the first place. The Capitol isn't a palace, congress isn't royalty living there, and we aren't their subjects.