For the French Republic, the separation between State and Churches is a pillar, a “marque de fabrique”, a distinction of the Republic.
France is proud of this distinction. French don’t pray God in Schools, Parliament, Army, Courts and others institutions.
Religions belong to the private life and can’t interferer in the public/civic life.

Debate of the law and the vote took place from the 21st of March 1905 t0 the 3rd of July 1905

Origins:
In 1516, the Concordat of Bologne is signed between Francois the 1st and the Pope Leon X. It limited the intervention of the Pope in the Church of France.

1682: Vote by the Gallicane Church of the Declaration of the Four Articles (temporal independence of the King, limitation of the Pope authority by the Councils and the customs of the King and the Church of France, possibility to contest the Pope decisions by a General Council)

1789: Article 10 of the Human Right Declaration recognised freedom of Religions, all religions.
The nationalisation (confiscation) of all Clerical properties, dissolution of all clerical congregations and associations were enforced, those involved in charity and teaching excepted.

1792: Secularisation of civil administration: marriage, birth certificate and death certificate became secular. Religious marriage became without legal importance.

1830: Catholicism stopped to be State Religion

1869: 1st appearance of the concept of Separation between State and Churches in the programme of Gambetta in the Programme of Belleville.

1879-84: With the Republic, heavy “laicisation” of France: no more compulsory of the Sunday break, cancellation of public prays, cancellation of the religious swear in court, laicisation of the schools, neutrality in public school in religious matters, laicisation of the teachers, law of divorce re-established, cancellation of prays in the Assembly.

1902-1905: Anti-Clerical politic of Emile Combes Government.

1905: Law of the Separation between the State and Churches (plural).

Modern developments:
1989: Polemic following the Islamic Hidjab.
1994: Religious symbols have to be discrete…
2004: All religious symbols are banned in schools.
2005: Commemoration of the 100 years of the law.

I don't see the danger of the seperation. With the talibans, Saudi Arabia, Pakistan I see the danger of State Religions.