Well, that's like saying if I murder a single person, then it's relatively minor compared to the work of a serial killer. In any case, I have no problem with someone making the case that the death penalty should be instituted for adultery, in principle, even though I disagree with it for the reasons stated. It's that I have found your tone to be very disturbing. Yes, we know that adultery is a grave sin. But can you find no room in your heart to have compassion to someone who may have sinned out of weakness?
Do you reject Our Lord's compassionate rescue of the adultress as inappropriate? Don't you think that He was speaking precisely to people of your mindset when he said that the one without sin should cast the first stone? In strict, justice, man, every mortal sin deserves the death penalty ... and not just adultery. But then we'd have to wipe out all but the smallest fraction of humanity.
If I would not have compassion on one who committed bestiality, incest, or murder, why would I have mercy towards someone who committed adultery? The Bible says that these people deserve to die. God is glorified through both mercy and justice. That is my view.
I do not reject the Lord's rescue of the adulteress, I see it as a particular act of mercy given to one transgressor. How ridiculous would this be if it became the universal standard? Justice would become a mockery on earth. All mortal sins which have been punished with death in Christendom should continue to be dealt with in the same way.
There should be no debate on this issue if you agree in principle that adulterers should be given capital punishment. My eager attitude should be irrelevant to the discussion.