To assume and assert that people who believe in God are less intelligent than those who do not is insulting, but you've apologized so it's water under the bridge.
The world almost certainly would be a better place if people didn't try to impose their ideas on others, but not all those who believe in God do, and not all who do, believe in God. You might as well say the world would be a better place if there was no violence. This too would be a very good thing, but neither of these scenarios is going to exist in our lifetime or the lifetimes of many generations to come.
It is quite common to blame religion for many wars and to assert, as you have, that we would have far less if we had no religion, but it seems to me that this is a very facile argument (no offense intended).
True there have been quite a few wars in which religious differences were the ostensible reason for conflict, but how many wars have there been solely because the act of warring was a tenet of a particular religion, or a means by which a group of believers worshipped their god or gods?
Much is made of Islam being spread by the sword, and to a certain extent it is true but Muslims didn't conquer people, force them to convert and then move on to the next town or village.
The Crusades were motivated by much more than the sense of a sacred duty to liberate the Holy Lands from control by believers of a false religion. Many crusaders were motivated by the spiritual rewards promised and for some it may have been their sole reason for participating but for the majority who took up the cross; the primary motivation was the promise of material reward and political power.
What leads to war? What leads to quarrelling among you? I will tell you what leads to them; the appetites that infest your mortal bodies. Your desires go unfulfilled, so you fall to murdering; you set your heart on something, and cannot have your will, so there is quarrelling and fighting.
Humans are a territorial species competing with one another for limited resources, and we are a social species so we act in groups large and small. Aggression is hardwired into our psyches and is triggered far more often by desire for necessary resources, material riches and the obtainment of power over others than it is by the commands of gods or their priests.
Religion had virtually nothing to do with the Revolutionary War, The War of 1812, The Civil War, The Mexican-American War, The Spanish American War, WWI, WWII, the Korean War, Vietnam or the first Gulf War. It had nothing to do with the French, Russian or Chinese revolutions except to the extent that in the first two, the Church was seen as an extension of the State, the Monarchy. The Persians didn't repeatedly invade Greece to impose Persian religious views on the Greeks, and Alexander didn't invade and conquer Persia and most of the known world to advance worship of Greek gods.
Genghis Khan, arguably the most successful conqueror the world has known, wasn't motivated by religion, and, in fact, religious tolerance was a fundamental principle in the manner in which lands conquered by the Mongols were ruled.
According to Charles Phillip and Alan Axelrod, writing in their Encyclopedia of Wars, there have been 1,763 major wars in recorded history and only 123 of them were fought over religious differences. Phillip and Axelrod estimate that only 2% of the overall casualties of all major conflicts were a result of "religious wars." I argue that all of these 123 wars had secular motivations as well as religious, and that in reality the secular dominated the religious, but even if they were all entirely motivated by religion, it simply isn't the case that we would "have a lot less wars" if there was no religion.
Spiritual beliefs may be a form of self-delusion, but it isn't necessary to that argument to mischaracterize their nature or influence on civilization. Certainly the priest caste in virtually every society throughout history has enjoyed the benefits of status and in many cases real power over people’s lives, and power that has frequently been abused. It also the case, though, that a great many individual members of this caste have provided great benefit to their fellows and to their societies in general.
It is important to distinguish between the tenets or teachings of a religion and the institutions that develop around practicing adherence to those tenets. It is rarely, if ever, the case that those within the institutions of major religions who abuse their power, adhere to the principles of their faith. I'm quite sure there have been madmen who have held power within religious institutions who done terrible things as a result of their insane zealotry, but they can hardly be said to represent true personifications of their faiths.
People are very capable of doing horrible things to one another and for many reasons that have nothing to do with their spiritual beliefs (self-delusional or not). Remove spiritual beliefs from the human experience and we wouldn't even notice an impact on the violence and destruction in the world caused by humans.