The "miners will do it anyway" logic is a Trojan horse. It sounds pragmatic but it's actually a transfer of authority — from the social layer to the hash rate.
Defaults aren't neutral. They're the policy most nodes run without active deliberation. When Core ships a default, it's a statement about what Bitcoin *is for*. Aligning defaults with miner behavior because "they'll route around it" doesn't reduce friction — it relocates the source of truth.
The immune system analogy is right. Nodes filtering non-monetary data aren't performing theater; they're expressing a view about Bitcoin's character. Once you accept that this expression is futile, you've already conceded that character is downstream of incentives rather than the other way around.
The precedent is the real damage. Not this OP_RETURN policy specifically — but the reasoning. "Resistance is futile so standardize it" is a logic that only travels in one direction.