My players generally don't assume elders are "pure evil" in the first place, in fact they more often think better of them than they've been given any cause to... but yes, my elders almost all have well-developed codes of conduct that they sincerely believe and follow. In fact, almost exactly the example you cite happened in my last game, although the Prince in question wasn't a "real" elder (less than 200 years old). The coterie had a captive, a Gangrel who had assisted the Prince's rival in an invasion attempt, and they started making hopeful diplomatic noises about gaining...