This is known as begging the question

To argue that we must decide who to tax more assumes first that we must in fact be taxing more. And that's the question that is being begged here:

The paradox is that raising taxes may scream “politics of yesterday” to voters Labour needs to win over, when in many ways the idea has never been so contemporary. Crumbling public services, a mountain of debt to repay, and an ageing nation of pensioners with a post-Brexit aversion to letting young, taxpaying foreigners move here all adds up to one logical conclusion: tax rises loom almost regardless of who wins in June.

For the aim, the current plan, is to deal with all of this by shrinking the size of the state itself. The declared targets - yes, stop sniggering at the back there - are that public spending should decline to some 35% of GDP, back where it was in the late 90s and also where it was for some goodly part of the post-war era. 

The current tax system can finance that without tax rises.

We do indeed agree that if you insist that tax revenues must rise then it is necessary to work out who should pay those higher taxes. But that first question must be answered first, do we actually need more tax revenue?

The answer to that being, currently at least, no, so therefore we've not got to fret over whose wallet to plunder, do we?