Enderman gets angry when a player look at him throw a spyglass

The problem is that enderman gest angry when somebody look at him throw a spyglass. Why is it a bug? Because when a player watch at an enderman through a carved pumpkin, the mob doesn't get angry on him. So when a player watch at an enderman through something, the enderman shouldn't get angry.

A video with the proof and the F3 menu is provided.