Well of course it's nice, no religion should ever interfere with the state. But you also need to keep them under control so maybe what France is doing is even better
As a non-religious person, I solemny believe politics and religion should be - and they technically already are - two different entities that should never interfere with each other.
I've never seen its use to "attack" Christians. They just don't want to see government funds used to support Christian or religious prograns, like putting the Ten Commandments in public schools.
Even for religions, separating religions from politic is a guaranty for each cult of respect for the freedom of believing in what one wants. Nothing is more intolerant than a religious state that says to people what to believe and repress those who think differently. A secular government must only impeach the excess of religious extremists.
Then you have the problem of saying what an extremist is. They blame Jews for killing Jesus, but given a choice between executing a man claiming to be God, leading a revolution against the state, or executing a common thief, who would you execute?
I think that church and government are two different and separated entities and each of them have their personal aims.
For this reason if it is true that the church mustn't interfere with the country's affairs the same is for the government.
Although I believe that the religious sentiment (in general, not only christian) is quite important for lots of people and so the country shouldn't be indifferent but tries to garauntee a peaceful cohabitation.