This argument just dismisses all criticism of the rules and implies that the "game" portion of the role-playing game is irrelevant.

If you truly think that, then I contend that you didn't understand their argument.

They are dismissing one specific criticism of the rules; that they can be "abused".

Roleplaying games are a collaborative social activity. The goal should be to collectively tell an enjoyable story. Under those circumstances, no one should have any incentive to abuse the rules or their fellow players.

In other words, criticising the rules because they can be abused is like criticising the design of a hammer because it can potentially be used as a weapon. There is basically no way to design a functional, effective hammer that does not open up the possibility that a bad actor could use it as a weapon. That does not constitute a flaw in the design of the hammer, and trying to redesign the hammer to prevent such an abuse will result in a very bad hammer.

There are bad rules and good rules, but good rules are good because they facilitate enjoyable play effectively. In other words good rules should help the GM and the players do the things that are fun. The rules do not exist to create a perfectly balanced showdown between equally matched opponents, and they cannot ever exist to do that in a context where you have a GM/DM, because the overwhelming power afforded to someone with near total narrative authority makes it impossible to ever balance that dynamic. Rather, the rules exist to a) introduce an element of chaos to the narrative, and b) guide the game towards outcomes that tend to reflect the individual capabilities and circumstances of the characters involved.

And within that context there are plenty of examples of good and bad rules design. You can absolutely find, make, or customize a better hammer. But if your criticism comes down to "You could hurt someone with this if you wanted to" then you have absolutely missed the point.

There is no set of game rules that will ever prevent a toxic table from being toxic. Despite OP's objections, the only solution to shitty people in your gaming group is to either remove the shitty people, or remove yourself. I get how much that sucks, but it really is the only solution.