I believe Jonathan's statement was correct in this regard. The  death toll under Stalin was larger than that within Nazi Germany before one has added in Mao's cultural revolution or Pol Pot. A generalisation it may have been, but Marxist-Leninism did seem to produce remarkably consistent results. The spectrum from Yugoslavia at one end to Russia at the other does offer some variety, but probably not enough to afford much in the way of rehabilitation.

The comparison with capitalism is valid in so far said economic structure has often had devastating effects (though the economic fall-out of communism was probably the least of its crimes). Nonetheless, it's probably not very helpful for a number of reasons, most obviously that fascism and communism were both mass movements, which capitalism has certainly not been since the nineteenth century. Equally, the spectrum of what can be counted as capitalism from Sweden to Hong Kong does seem to afford rather more diversity than can be said for communism.