When spammers pay large miners directly, it does hurt decentralization of miners. And I think that is bad, but I compare that downside with this other downside: when spam is "welcomed" by removing the spam filters, that increases the total amount of spam on the blockchain, and that hurts decentralization of *nodes.* Specifically, it makes nodes harder to sync, and incentivizes more people to avoid doing so. So either way you get a harm: if spammers pay large miners directly, that hurts decentralization of miners. If, instead, they are welcomed into the public mempool, that amount of spam on the blockchain rises, and that hurts decentralization of nodes. Which harm is worse? I think the latter is worse, particularly because the *amount* of money actually going to large miners from spammers paying them directly is currently very small. The filters seem to be effective enough that most spammers aren't *trying* to bypass them by paying large miners directly. Instead, they seem to prefer just using other blockchains where spam is more welcome.