I know you were just making a turn of phrase; the real point is assuming that everyone who walks up to your door might be there to kill you is paranoid.
I certainly don't assume that. FWIW, I don't even have a fence, and the mail carrier walks up to my door five days a week without issue.
If the gate is open, feel free to walk up to the door. If the gate is locked, it's trying to tell you something (and it isn't "hop the fence"). If the door is locked, it's saying the same thing: "No."
I get that people might have legitimate reason to be at my doorstep without "permission" but I can't really think of any legitimate reasons for bypassing a lock (unless you're the Fire Department).