As a general rule I avoid unnecessary conflict. The first time the clerk(ess) told me I was wrong, I would apologize for the sake of politeness, leave, and never return.
There are hundreds of millions of laptops, and I can live without the one I would have bought there.
The day will come when one either uses the pronouns or dies. At my age, I would rather die. If I were younger, the other person would die; that’s usually what happens in war.