"If you don't consent to the idea of someone doing A to you in the reversed situation, then you ought not to do A to another"
"If you don't consent to the idea of someone doing A to you in the reversed situation, then you ought not to do A to another"
We need a don't-combine form, not an if-then form.
"If you don't consent to the idea of someone doing A to you in the reversed situation, then you ought not to do A to another"
Suppose that you're a Nazi and don't consent to the idea of someone letting you live in a reversed situation in which you're Jewish. The formula would then entail "You ought not to let this person live." But this is absurd!
The possibility of such fanatical desires ruins if-then formulations of the golden rule. The don't-combine formulation is better.