Mojang seem to be forgetting that it costs money to operate a server, and a "freemium" model is a completely viable and legitimate way to fund that operation (other ways such as accepting donations and paid-players only exist).

Some may say you are in essence paying a third party for Mojang's work, when in fact you have already done so by purchasing the game in the first place. What position do Mojang feel they are in to dictate how people play the game?

Ultimately it comes down to what players want, players are not afraid to vote with their feet and abandon servers which operate in this way; as of yet there seems to be no widespread trend in abandoning these servers.

As an aside, I believe this is more likely a push by Mojang to shut down paid servers and move people onto their Minecraft Realms product which does exactly this.