I never understand tax stuff - but as I understand it, the money concerned wasn't personal income available for use on personal expenditure, it was political income, reserved for expenditure on political activities such as employing political workers. No different in principal from a lawn machine maker using money from selling lawnmowers to employ people to make them for his company.

Perhaps the money taken in by companies like that should be taxed at the same rate as personal income, but that's not how it's done. I can't see how it can be seen as a tax fiddle, using loopholes in the law, like a company setting up a fictitious branch overseas where tax rates are lower.

The criticism seems to be assuming that political activity is a luxury hobby, like playing golf or buying yachts, and that taxed accordingly.