Re: The article author is part of the problem.
'They do pay their employees though, and their employees pay income tax. In fact in most cases the employers pay the income tax on their employees salaries "as they earn".'
First sentence correct, second sentence incorrect. It's much the same as VAT; they're tax collectors, at their own expense, on behalf of HMG. They're also tax collectors on behalf of HMG in respect of employees' NI contributions. But they do pay employer's NI.
However it's fair to say that they are responsible for generating income tax and VAT by providing employment and selling stuff. They will also be spending money on goods and services which will also result in income and corporation taxes (they'll also be charged VAT but this will be offset against the VAT they collect).