There are different kinds of people who will have very different reactions when they encounter this sign. One type will regard it as some sort of existential challenge and act accordingly, with quite messy results that will irritate the hell out of the store manager or late night cashier. There are also those who will just read the sign, laugh, and take their half gallon of milk to the check out.
Then, there are the Republicans. Their immediate reaction will be one based in stone crazy QAnon-style conspiracy. With Republicans, conspiracy theories are now their lifeblood; the crazier the better. Conspiracy courses through their veins like some new strain of highly adaptable e coli. A Republican will read that sign and wonder: "Just what are they hiding back there? Planned Parenthood's harvested "baby parts?" Is this the secret entrance to where the libtards have the clubhouse for their local chapter of the Hillary Clinton child sex ring? Are there pedophile parties going on in there just behind that fake stainless steel back wall that's really a door? Is that where the store keeps the babies the democraps eat? Is that where the Libs keep the slave children that they're about to ship off to the child labor camps on Mars that Rush and Sean and Alex Jones talk about?"
So, if you're in your convenience store and you see some typical soul-impaired, dead-eyed republican just standing there by the milk fridge lost in what passes loosely for thought, just say excuse me, reach in, get what you came for, pay the cashier, and high tail it out of there before Mr. Vanilla ISIS makes up his mind to "set things right" and go out to the parking lot for his AK-47 "deer hunting" rifle and a bag of extra clips.