That's just an a priori assertion that certain means are categorically unjustifiable (by anything, ends or otherwise) because they are inherently unethical, which is irrelevant to the form of the argument.

If you want to make the point that certain means are categorically unacceptable, make that argument (which will very quickly, I suspect, get to a root moral axiom on which no debate is possible, simply agreement or disagreement) rather than raising irrelevancies about the form of the argument.