Actually, it wasn't Christians protesting [1] the Bible-burning. It was Muslims protesting an alleged desecration of the Qur'an.

"Muslims protest alleged Koran destruction in Greece," from [2] Reuters, May 21 (thanks to Alexandre):

Hundreds of Muslims marched through central Athens on Thursday, damaging shops and cars, to protest what they said was the destruction of a Koran by a Greek policeman.

The president of the Muslim Union of Greece, Naim Elghandour, said that during police checks at a Syrian-owned coffee shop on Wednesday, an officer took a customer's Koran, tore it up, threw it on the floor and stomped on it.

In response, about 1,000 immigrants, many from Syria, Pakistan and Afghanistan, marched to central Omonia Square, smashing several shop windows and five cars, a police official said....