To answer the question posed by the OP. If I have my gun on me, it's concealed. Because I'm about to leave the house(thanks, Texas /sarcasm).
Very rarely does anyone see my sidearm. When I answer the door and don't know who it is, I usually ask 'who are you and what do you want?' One time I had a bill collector come to the house, I was outside on the porch with my brother in law. I asked them who they were and what they wanted, they did not answer appropriately, instead simply responded by asking for my mother. I got up to intercept, but they pushed past me and headed towards the door. Which was open and screen unlocked for obvious reasons. Fortunately for the bill collector, my mother got to them before I could. But had she stayed inside, things would have gotten pretty ugly pretty quickly.
This is MY house. My mother, sister and brother in law live here. But my sister and brother in law are guests and I am the head of house hold. If you ignore my questions, if you continue towards my door and move past me. You are asking for trouble. I would have only informed them that they needed to leave once. Barring that I would have immediately called the police. I don't care who you are. If you do not respect me in my home, then you are not welcome here. If you do not leave when I ask you to, I will call the police. If you are still here when they arrive, you will be arrested. If you leave, I will file a report. If you cause any trouble or pose any sort of threat, I will inform you that I am armed and ready to use lethal force in the defense of my home and family. It is a particularly bad idea to ignore my questions and insist on seeing my mother. She has had numerous stalkers, she has been kidnapped, beaten and raped. And that man is still out there looking for her. So by coming to my house, inquiring about my mother, and refusing to state your name and purpose for your visit, you are automatically deemed a threat.
To add on to that, my mother had asked the person to leave, and they refused multiple times. Instead the collector insulted my mother and only opted to leave once I stood up and made my way over there.
In summary. I can be pretty rude when I answer the door. But you better comply with my demands. Do not forget that you are a guest on my property and I have every right under the law to demand your withdrawal. Failing to abide my wishes to leave, you will be arrested, further persistence and aggressive behavior will be met with force. Do not trifle with me, I will crush you.