From the beginning politics and religion are nearly the same thing. You can look at written history starting way back with the Pharoahs. The world has been changing (and improving) since the discovery of grain and farms. So many years ago a person expected to spend most of their time working, then getting sick, then dying. A boy hoped to live to be 30 or 40. A girl hoped to survive bearing children. Food was terrible. Medicine was relatively useless. Wild beasts were a threat and could only be countered by strong hunters. Diseases were inexplicable. People wondered if life would go on dreary and terrible as it always had. Enter the early politicians. A politician spreads hope like candy and makes all kinds of promises. They'll literally promise anything as long as they don't have to come up with it immediately.
Since that time religion has gone through various phases. From time to time people decide to make positive changes, and these changes get incorporated into their political and religious lives which are not actually separate things. Good ideas don't get integrated easily. We resist change. We say "We've done without that for ages and ages, so we can keep doing without that. We don't want to think about it."
Sometimes a generation wakes up and is unhappy with the way things are and criticizes what a previous generation has done. Often it is in ignorance of the past. The innovations this generation makes may be criticized by future generations as regressive. So it is that people criticize 'Religion' today while continuing to be as religious as ever. The Democrats are a religious group as are the Republicans as are the Socialist Party, Labor and the Conservative Party. These are all religious. The US Constitution is a religious document. Our courts are religious courts, relying always upon precedents, prestige, gorgeous expensive buildings with a special priesthood of lawyers which are gradually replacing other religious priesthoods.
So...that's why.
That is a modern religion. An ancient religion would have encouraged you to dominate others for the sake of your family and tribe. A modern religion can turn nasty though. We are all sensitive to the general push of society and can get carried away as if in a fast current.
...or "You're an idiot because you voted for XYZ. Don't you understand B about A? What the bleep is wrong with you?"
