In some countries even government propaganda is not free , you have to pay for a license to watch it.
The argument for it however is that they can publish content which has negative commercial but high civil value. Commercial run stations cannot and will not publish content or views which will harm their sponsors, investors.
There are many, many, many examples of them (the BBC) doing just that internationally. They can and will go investigating into deep dark holes that "investor funded" journalists will be told to steer clear of or be sacked.
Where I personally feel the issues begin is not with the propoganda, which is there, it's the "other commercial interests" of the BBC.
Example: Doctor Who. The resent series have, argued by some, been produced specifically for a US biased international market and not infact made for the british public which funded it. The BBC then "sell" that content to the US. They argue, commercial revenue streams are always part of the business model and the tax payers will benefit from teh revenue collected.... But ... the content suffers.
Looping back to the original point though... the TV licensing laws are just not compatible with modern media or how we consume it.