Simply saying you don't have to buy them doesn't even correlate to their problem with it.
It is that if they want everything in the game they have to pay a sub fee and pay extra for other things. Yes that is if they WANT to, but not the point.
In the past it was not this way, it has morphed into this over time. F2P had micro. P2P did not. No doubt they are taking notes from Blizzard.
I care not either way.
But neither side is wrong on this, it is their opinion on the matter.
Again, just because they are not FORCED to buy it, doesn't alleviate what their concern is. The concern is that they don't get everything for what they already pay.
A legitimate concern, as much as it doesn't bother you is a legitimate feeling.