One phrase is what the US Congress uses to describe the actual, existing tax [0], the other is a phrase created by opponents of the tax in the 1940s [1]. Only one of these words looks charged to me.

[0] https://www.law.cornell.edu/uscode/text/26/subtitle-B/chapte...

[1] http://www.npr.org/sections/thetwo-way/2010/12/16/132031116/...