No. William grew up at a time when the Kingdom of Jerusalem was strong and was Archbishop between 1127-1135. At no point was William ever in danger from Saladin. Saladin actually captured very little territory from the Crusader states until 1187, when a decisive battle was fought and he captured most of the Levant. William would have had reason to fear him then, but he had passed away the previous year.

Also, Saladin did not sell anyone into slavery as long as they paid a ransom - a measly 10 dinars. Anyone who paid was allowed to leave Jerusalem with all of their possessions. When the Patriarch of Jerusalem tried to leave the city weighed down with treasures, Saladin was advised to keep most of it but he took nothing except the 10 dinars and let the Patriarch leave with the rest of his wealth. Saladin did not want to break the promise he had made - that anyone who paid the ransom was free.