Are you playing dumb?
The argument is about whether people play on private servers just cause it's free. Meaning, if private servers didn't exist, these people would play on retail. They only played on private servers because it meant they didn't have to pay money.
That argument holds no weight, when there is a way to play on official retail servers without having to pay money. Is that maybe a term that you like better? They don't have to pay money in order to play.
When you say that "however indirect that purchase was doesn't matter" all you show is that you don't get the initial argument.
Why would it matter who paid for my sub, if all I want is to play without paying money?
Please, see some sense.