Why was toleration so difficult?

Marburg Colloquy, 1529
Martin Luther
Ulrich Zwingli
John Calvin (Geneva)
Transubstantiation
idolatry
heresy

Coronation Oath
1. Protect subjects in body and property
2. Defend the church and Christian doctrine
tyrant

Affair of the placards (1534)
Huguenot
Calvinism
martyr

regent
Catherine de Medici
Admiral Coligny

Guise (Lorraine, Catholic) Valois (ruling dynasty) Bourbon (peers, Huguenot)
Duke of Guise Henry II (d. 1559) Henry of Navarre
Cardinal of Lorraine Francis II (d. 1560) Duke of Condé
  Charles IX (d. 1574)  
  Henry III (d. 1589)  

French Wars of Religion (1562-1594)
St. Bartholomew's Day massacre (Aug. 24, 1572)
Edict of Nantes, 1598

tyrannicide
regicide