I couldn't have put this better, so I won't try. It's by Jenni Russell in the Guardian:

Within hours of last week's announcement of audacious Tory plans to cut inheritance tax and hit the foreign super-rich instead, Labour figures were explaining to me why such proposals were wrong in principle as well as practice. You couldn't, they said, be a party of fairness while allowing the already privileged to hand on hundreds of thousands tax-free to the next generation. To do so would only entrench the gap between the children of homeowners and those without any capital behind them. Nor could you tax the non-domiciled effectively. That was too complicated and ran the risk of driving out foreign wealth creators.

As for many of the rest of the Tory proposals, too, could be challenged on grounds of principle. Take marriage allowances. There should be no privileges for the married, whose children already did better on all counts. Labour's policies, instead, were aimed at levelling life's playing fields. So the financial help for single parents was a socially just response to the disadvantages their children already experienced.

A week on and those arguments are in tatters.

I agree. Principle matters. And the Labour Pre Budget Report is entirely without principle.