I think from a social point of view lack of organized religion (nothing against spirituality in itself) is better, since organized religion is often used as a way to control people and put them against one another, often pushes to get religious dogmas into law (see the catholic church here in Italy as a prime example), and so on
Well that's on a religion by religion basis.
Any ideology could be used to control and manipulate people. Take, for example, Hitler who used his Anti-Jew rhetoric and his Nazi ideology, he used that to manipulate the German people and kill 9 million innocent lives, was that his Christian beliefs or his Nazi ideology?
No offence, but to suggest that religion is only ever used to get other people to kill others is ignorant of all the good religion has done in the past. If not for the Islamic Caliphates centuries ago, the majority of Aristotle's work would've been burnt away, this is just one of many cases where a religion saved something, in this case the culture and works of the Ancient Greeks who were denounced by the Catholic church at the time.
Islam is more of a way of life than Christianity is, so I can only really speak from experience in saying that not all religious dogma is evil and oppressive. One must also consider that humanity is inherently a violent species if we have anything against each other we'll use whatever beliefs at our disposal to fight each other. Only in the last century did Mao Zedong kill more people than Christianity and Islam
combined.
Edit: Forgot to mention this, but look at the politics of western nations, people hate each other because of their political views, and will call them names based on them, just even more, evidence than any ideology leads to hate.
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Religion is really a mixed bag. On one hand, it is used all the time to control, brainwash, excuse acts of terrorism, etc but on the other, if done right, it can create amazing communities, lead people towards good moral values and make a positive impact on the world. However, I think nations having an official religion is horrible, and its pretty shocking so many major nations still do.
Why, exactly? I can see it being an issue if the majority of the population do not follow it.