To critique them you gotta understand them. A section of the society believes that the criminals need to be re-educated instead of culled. This belief is somewhat true is some crimes, say stealing, fraud etc. But these guys tend to forget that the biggest fear in this world is fear of ones own life. that is why murder has the punishment of death. You take another person's life. You pay with your own. period. Unfortunately, some people blurr the lines of these crimes and believe that criminals who have committed murder etc can also be re-educated and re-introduced in the society. Hence, you see these guys pointlessly debating on the demerits of death penalty. And since death penalty is in Islam which is an anathema to this section of the society, their stance if further hardened.
They do not necessarily want the criminals to go Scott free unless it is one of their own. They want them to be re-educated and re-introduced in the society as productive members. They do not realize that we do not have the resources or the time to carry out this fancy idea. hence, you see them arguing against death penalty without really seeing the ground realities.