Emperors of Rome were notorious for persecuting religions…Everybody is familiar with Christians being fed to the lions in the arena, but there were also Roman emperors who made it illegal to worship the old pagan dieties and would punish those who retained that faith. Sometimes by death

The Inquisition in the Middle Ages (especially in Spain). It was a tribunal set up by the pope to fight heresy. It’s the perfect example of what happens without freedom of religion

It is the same with all religions when they become linked to the state power.
They abuse their position to eliminate all rival faiths.
If you stand on a street corner in Israel or Saudi Arabia and try to preach about Christianity you will be arrested and deported or worse.

Freedom of religion is not important what is important is freedom from religion. The best example is the break down of the catholic church during the late middle ages. This loosening of dogma allowed the renascence period to happen which was the first step of the technological/social change boom we are still riding.
Contrast this with Mohamed’s uniting the Arabian peninsula and launching the Muslim religion. They are still stuck in the dark ages.
After the fall of Rome the Catholic Church took awhile to dominate Europe. Once in control the church stiff led society for centuries. The crusades and the inquisition are examples of it’s style.

The Holocaust. Being Jewish was punishable by imprisonment, torture and death.

The Crusades.