These 4 happy conditions no longer exist. The moral evil of confiscatory tax rates aside, low marginal tax rates are now utterly necessary (as well as a number of other things) for the US economy to resume flourishing.
Insofar as your leftist acquaintances are working, whether they admit it or not, for the destruction of the US, they will perforce also support higher marginal tax rates.
Exactly. Not much job outsourcing going on back then either.