The license fee is impossible to enforce
The only purpose in making something mandatory is if there are real consequences for not doing so. The license fee is impossible to enforce. It is therefore pointless being mandatory.
The simplest way the BBC could enforce the mandatory payment of the license fee in the digital era would be to reconcile everyone’s BBC IDs that are used to watch BBC iPlayer and compare that list to the list of people with a TV license. They are both run by different organizations and are not designed to be integrated in this way. Alternatively, the BBC could monitor internet traffic. This would jar with data protection laws and require assistance from the Home Office. In a democratic nation, citizens have certain privacies protected by law and If the BBC were to access internet traffic, or track users' television or internet behavior in order to enforce the license fee, it would morally and legally conflict with citizens’ privacy. If the law can’t be enforced anyway, only those who choose to are paying the fee. This is essentially a donation so instead, they could make it a volunteer fee and do away with the ineffective system. This could actually lead to more revenue since a lot of people would support the decision to get rid of the mandatory fee.
It isn’t arbitrary if it gets people to pay. There doesn’t need to be a way of enforcing it if the threat of enforcement is sufficient to get people to pay. The TV licensing authority already sends letters to those that haven’t bought a TV license threatening a home visit. For those consuming the BBC’s content or live broadcasting without a license, this is often enough to get them to pay.
There is no purpose in making something mandatory if it cannot be enforced.
[P1] Something should not be mandatory if it cannot be enforced. [P2] A mandatory BBC license cannot be enforced. [P3] Therefore, the BBC license should not be mandatory.
Rejecting the premises
[Rejecting P1] Something can be mandatory even if it cannot be enforced. The act of making it mandatory means more people will do it, regardless of enforcement.