Why the turn undead hate? Well, let me tell you about our 4e cleric.
The player said "I want this cleric to be an undead hunter and healer". He had an objective and an image of what he wanted. Good for him. So he tralled every feat he could get, picked the right god, got as many extra channel divinities he could yada yada.
Well, we had two undead fights in particular and hit an interesting problem. As a DM, I found myself wondering what the point of using undead was. This character had SUCH a profound effect on the encounter that undead had become...irrelevant. It was nigh on pointless including them, unless I put so darn many in or deliberately doctored the encounter against the character (For the record, I didnt do either of these things, its just bad DM'ing). So, the undead encounter just stopped.
The player ended up upset because there wasnt enough undead encounters, so I put in some tokens just to keep him happy. What the? One of the most iconic monsters in the D&D (nay Fantasy) spectrum reduced to marginal, pointless side encounters? I was not at all fond of this situation.
But it wasnt the players fault, nor was it the 4e cleric necessarily. It was the concept that the subset of creatures should consistently fall victim to such potent capability confined to one class. You end up with
a) undead fight, with reasonable numbers of opponents and undead on par with other creatures, with cleric in the party = white wash the enemy
b) undead fight, with reasonable numbers of opponents and undead on par with other creatures, with no cleric in the party = appropriate challenge
c) undead fight, with un-reasonable numbers of opponents and undead above par compared to other creatures, with cleric in the party = appropriate challenge
d) undead fight, with un-reasonable numbers of opponents and undead above par compared to other creatures, with no cleric in the party = far too challenging
So either undead are too hard to handle and you MUST have a cleric, or they are perfectly well thought out but pointless if you do have a cleric.
Turn undead has never made sense to me, and doesnt start making sense till you start reigning in its power/