As for levies on externalities, these should be more accurately seen as correcting a market failure, the social cost that society must pay that the consumer/producer do not pay.
Notably, Frank Ramsey and A.C. Pigou can be considered crypto-Georgists -http://blog.lvrg.org.au/2013/09/ramsey-and-pigou-crypto-geor...
"As we shall see, Ramsey not only formulated a rule that leads directly to a “single tax” on land, but also anticipated the so-called Laffer curve in cases where the “single tax” is not employed. Moreover, Ramsey's rule was to be applied after any externalities had been internalized by means of appropriate taxes and bounties."
Georgists are a bit like libertarians when it comes to income taxes. It's very difficult for government to demonstrate a moral basis for interfering in work markets to generate taxation. Libertarians argue that if you are forced to pay 57% income tax you're 57% a slave. I'm not sure Georgists would go that far, but it seems unlikely you'd see implementation of taxes that are both economically less efficient and ethically more dubious than taxation of economic rents.