Why is religion so repugnant to some people

[Tonus]

I can see people not believing in God but why hate it?

There are aspects of religion that are harmful to both the people who practice it and the people they deal with. Primarily, the belief that god demands or expects certain behaviors or actions regardless of circumstance, on pain of horrible punishment or the missing out of a fantastic reward. This leads people to deny urgent medical care for themselves or their loved ones. It leads them to ostracize friends and family and destroy close relationships or beneficial arrangements that can have a ripple effect. It leads them to depend on a nonexistent person to solve their problems in lieu of action, and it leads them to credit that nonexistent person on those occasions when things turn out well in spite of their lack of effort.

And this is not to mention the people who take even more extremist routes, to the extent that they deliberately cause mental and emotional anguish to others, or even physical harm. The people who assault (and even kill) gays in the name of their deity are acting on that same primary impulse, and they can whip up a few scriptural verses to defend those actions. Religion can warp people in any number of ways. It is like other forms of tribalism (racism, nationalism, sports fanaticism) with the very dangerous difference that it claims the highest possible moral sanction of all.