The Spam Apologists’ concern about UTXO bloat, block propagation, and private mempools/APIs are trivial when compared to concerns about the fundamental integrity of Bitcoin as a Sound Money and Sound Price Signal protocol.
Spam distorts Bitcoin’s native price signaling mechanisms.
It distorts fees and it distorts the Difficulty.
Obviously, price distortion leads to sub-optimal economic outcomes.
Anyone who took Econ 101 knows this.