The death penalty is a very complicated subject to deal with. Most people would not want to talk about it out in the open. It is not a light subject to deal with in the first place. It is definitely not what one can talk over the dinner table. Since the lives of people are at stake, the matter is very serious and people understand it. That is probably why they hesitate to even talk about it freely.
Regarding the question about the effectiveness of death penalty, we first need to understand its purpose. Basically, it has two motives. The first one is to punish criminals for their guilty acts. The second motive is for it to serve as a warning to others and to prevent them from committing the same crimes.
While some people believe that death is the best punishment for severe criminals, there are better ways to deal with them which could be more constructive in the long run. There have been many instances in prisons where hardened criminals have become totally new people after being exposed to the scriptures and moral instructions. So, it is wrong on our part to think that hardened criminals would never turn over a new leaf.
Regarding the question of the death penalty serving as a warning and a preventive measure for others, we can never be really sure about how many people it has stopped. While we can only count the number of incidents that have happened, we can never count the number of incidents that were prevented from happening. So, we will never know about the effectiveness of the death penalty in stopping crime.