Many Muslims say that people who leave Islam shouldn't be killed, but many say they should. This Islam Q and A (Question and Answer) site explains the "good" reasons why.
We also say that the death penalty exists in the modern laws of man to protect the system from disorder in some situation and to protect society against certain crimes which may cause its disintegration, such as drugs etc. If execution can serve as a deterrent to protect man-made systems, then it is more appropriate that the true religion of Allaah, which Falsehood cannot come to it from before it or behind it [cf. Fussilat 41:42], and which is all goodness, happiness and tranquility in this world and in the Hereafter should punish those who commit acts of aggression against it and seek to extinguish its light and defame its image, and who fabricate lies against it to justify their apostasy and deviation.
Not Muslim Anymore replies:
So all apostates lie about the religion? How does leaving Islam and stating what you think about it relate to the death penalty in modern laws? That is for murderers, not people who want to change their religion!
This is the most ridiculous thing I have ever read!
Islamic "logic" tends to get that reaction.