Gary Lineker is right to remind us that the UK's TV licence fee — which funds the BBC — is a tax. Although not officially described as a tax until 2006, it was effectively one long before that.
My district council charges for providing and emptying a brown bin used for garden waste. This is analogous to a commercial fee: I choose whether to pay the charge, in exchange for a specific service. The TV licence fee may have had a similar character when it was introduced in 1946, but after non-BBC channels arrived in the 1950s, so that the revenue raised by the charge became disconnected from the services used, it effectively became a tax on TV sets.
Whatever the pros and cons of using taxes to finance a public broadcaster, the administration of a tax should be managed by the state or an agency of the state. Control of TV licensing should never have passed to the BBC, as it did in 1991.
The debate over free licences for the over-75s is embroiling the BBC still further in matters that should be the province of the state. The government should not have withdrawn funding for this in the expectation that the BBC would work out its own concessionary schemes. If the BBC becomes responsible for means-testing, it risks taking on even more quasi-governmental functions.
If the license fee is retained, it should be as a conventional tax, as for vehicle licensing, and it should be administered by the state. The people who call at your home to quiz you, or attempt to prosecute you, should be members of the state apparatus — not employees of the BBC or one of its subcontractors.