I'm not talking about 'spiritual blackmail', but real, mortal danger. The standard sentence for renouncing Islam is death. The standard punishment for offending Islam is death. Not hell, not Allah's displeasure, but real death. Execution, when they can get away with it, assassination if you are in a non-Islamic country. There have been other religions, including Christianity, which have practiced similar penalties in the past. The leaders of these religions are not concerned with any spiritual punishment, but with maintaining control, and in many cases the only way to do that is to kill those who do not agree with them.
As an atheist, I deny the existence of gods, I deny the existence of an afterlife. Therefore religious leaders no longer have and 'spiritual blackmail' with which to try to control me. In much of the modern world, of course, I am protected by the same laws which protect those who practice religion. But in some parts of this world, simply denying the existence of the local gods is punishable by death. Simply speaking against the religious leaders is punishable by death. Obviously these religious leaders have no faith in the 'spiritual' punishments of their deities, and resort to physical punishments as a means of maintaining control.
ANY law which helps to reduce that stranglehold is, in my opinion, a good law. It does nothing to harm the followers of any religious cult, but does weaken the power of the leaders of those cults. It is the leaders of the Muslims in France who are most threatened by this law, not the women who will be liberated by it.