I think (hope) attitudes are changing on this. 15 to 20 years ago it was assumed in management circles that scanning for open ports was nefarious. These were the people who believed in security by obscurity.
These days I hope people realize that the equivalent of "lock the front door, but leave the back door open" isn't viable.
Also, the door analogy is (as other commenters have pointed out) flawed. Should an open port be translated as a door you can knock at or ring the bell, a door you can open, or just a door you can see. I personally agree that "An open port is a door on your house" but others see it as one you've just knocked on, and others see it as one you've willfully tried to break into.
The informedness of the port owner will define how they interpret the port scan.
These days I hope people realize that the equivalent of "lock the front door, but leave the back door open" isn't viable.
Also, the door analogy is (as other commenters have pointed out) flawed. Should an open port be translated as a door you can knock at or ring the bell, a door you can open, or just a door you can see. I personally agree that "An open port is a door on your house" but others see it as one you've just knocked on, and others see it as one you've willfully tried to break into.
The informedness of the port owner will define how they interpret the port scan.