Quoted:
Yes it is.
There is a certain degree of expectation of what you bring with you when you enter a person's home. You should tell them, so they can be informed as to the conditions you bring with you, so they can make an informed decision with all available information. A person's home is their controlled space, and you are entering it.
If the home owner had a live alligator in their bathroom, would you want to know about it? Or should the homeowner just "let you figure it out, cause it's not your business"? You have a expectation that the bathroom does not have alligators in it, don't you? When you are invited over, it is assumed your are not knowingly bringing a deadly contagious disease with you, and the home owners is not expect to need to ask.
Now if they homeowner know you carry all the time, then he sould expect you to be armed when he invites you over.
I'm not sure that is an apples to apples comparison.
The question isn't "is it wrong to go into someone's house spraying bullets aimlessly towards everyone in the area?" If you want to say that having a gun on you isn't the norm, then you'd probably be right. That disease reference sounds kind of like being in the presence of a gun = instant death. Same with the alligator; guns are not autonomous killing machines, alligators are.
What can we take in a person's house without asking? How about a pocket knife? Mace? Box cutter? Koran? Is the line drawn at firearm? I'm as curious as anyone else. I understand that keeping secrets isn't the best policy, but neither is creating a concern where there isn't one.
We all obviously respect firearms for what they are capable of, but we all also realize that they are useless without an operator. There are literally thousands of things you could take into someone's home that they would be concerned or offended by, but that we would never give a second thought to. The difference is that those things aren't as politically charged as firearms.