Comment by Analemma_

> Liberals vehemently opposed the idea, calling it 'regressive', meaning it would be socially backwards,

That's not what "regressive" means in the context of taxation. A "regressive tax" is one that takes a successively higher proportion of your income/wealth the poorer you are, while a progressive tax is one which takes a higher proportion of your income/wealth the richer you are. This is standard vocabulary in economics.