Just tell him that power centralization under corporate capitalism is precisely, the reason why corporate hierarchies are as vertical a hierarchy as an empire of old, specially so when compared with the democratic nations they usually operate under.
Just tell him that worker co-ops, which can still operate under a free market legal framework like Grupo Mondragón, are definitionally less vertical because their organizational structure, DECENTRALIZES OWNERSHIP away from corporate style owners and investors/shareholders, into the work force that makes the enterprise to work and be something to invest on in the first place.
Private owners still get to delegate and make money without working, they just can't earn more than a set amount of times than their average employee, and don't posses divine control over what the company produces, meaning nobody is expropriating anybody, and it's not a redistribution when the labor surplus is being stolen*, you go live in N. Korea and experience the verticality of its pseudo-soviet, state capitalist, hereditary monarchy)
The USSR was too vertical for anarchists, and to be fair, most people considering socialists today.
Co-ops are more horizontal and they operate in a more similar way as the democratic government they might be operating under.
Anarchism is the current of critical thinking that analyzes human hierarchies, but I guess that Lobsters having a reward mechanism in their nervous system, just like every other single animal in the world,
Just give them the basics and let them mald, cope and writhe, for each wincing is an argument in your favor.
*If they try to talk the slightest smack about labor theory of value, ask them what superpowers do entrepreneurs have, that don't require the labor of either scabs or robots to turn time and resources into marketable products.
*If they cry inflation, ask where the CCP thugs breaking Japan's legs for operating under a national debt of 300% of its GDP, without needing not even half of the "Austerity" measures that every other capitalist country has gone through, for literally nothing because money is not a natural resource, it's a construct of the mind materialized into cheap, almost endlessly replicable tokens, because it's more intuitive than bartering, which is rendered obsolete the moment your society gets more complex than neolithic communities of farmers bartering food, in exchange for tools with of metallurgist communities.
We do, live in a society...