But isn't this a true of the supralapsarian position? Aren't you assuming that all Calvinists are infralapsarians?
No, there are two problems here:
1) Just because SOME Calvinists may be "supra" doesn't mean you can broadbrush Calvinists" based on that. It would be as errant as saying, "Christians hold to determinism", based on the fact that SOME Christians are Calvinists.
2) Secondly, as far as I understand, Supra's still believe that the reprobate are all sinners, and eternal damnation is BECAUSE of their sin. The logical order doesn't alter that fact.