I've been thinking about your question bags and here are my thoughts.
We evolved to live in tribes of a few dozen people with an extended network of contacts of no more than low hundreds. We are naturally interested in people and want to know what is going on in the lives of our friends and relations. This may be a particularly female trait. I think gossip magazines etc may fill this void in modern society where so many people live in rather anonymous cities.
Also, in the context of a small community, healthy, attractive females that are outside our social group are at the same time very interesting (good genetic partner for our sons?) and threatening (will they seduce our partners or sons away?) . Hence, maybe, the contradictory comments made about celebs plays into this.
And finally,
We all have within us the capacity to be good, kind and altruistic and we also have the capacity to be mean bullies that try to crush those lower in the pecking order, or on the fringes of the group. What is expressed in terms of actual behaviour is largely "nurture", experience and cultural norms we live in.