Spyglasses Should Not Anger Endermen

While I was exploring the End, I tried to use a spyglass to look for an End City and angered a bunch of Endermen.  After that happened, I wondered why they got angry since when you look through a spyglass, you look through glass.  When you look at and Enderman through a glass block they do not get angry.  This is not a big deal, I just think that looking through a spyglass should not anger Endermen, since it would make the game more consistent.