According to St Paul, we do not do evil that good might come of it. A plausible version of this principle is:
- It is wrong to intend to produce an intrinsic evil, either as an end in itself or as a means (causal or constitutive) to an end.
Presumably, a standard Calvinist response will be that (1) applies to us but not to God. However, our ethics is supposed to be an ethics of love, and God, whether necessarily or by his contingent decision, always acts in love as well. (Some Calvinists think God doesn't love the reprobate. But the argument still applies insofar as on Calvinist views it seems that God intends the elect—whom he loves—to sin, in order that he be able to redeem them.) And principle (1) seems to be at such a high level of generality that if it follows from the duty to love in our case, it is likely to follow from that duty in the case of God, as well.
I think the Calvinist should deny that God intends sin. Instead, the Calvinist should give some sort of a Double Effect story on which God causes something that entails the existence of sin, but which is distinct from the sin and good, and to which the sin is not a means. Maybe instead of willing Sally to punch George, which was evil, God can intend Sally to swing her fist forward, which is not in itself an evil, but which, along with the other things God has willed, entails that Sally is punched by George. Then one ends up denying that God intends people to sin for the sake of his glory, instead asserting that for the sake of his glory he permits them to sin, while he (God) wills something that entails their sinning. Whether it is possible for a Calvinist to walk this fine line is not clear.