Religion is a product / function of the human mind. It causes people to perform meaningless religious rituals, which have no basis in reality (they are pointless)
Freud's theory that the male child has an unconscious desire to kill his father and have sexual relations with his mother, which gets repressed into the unconscious mind
Freud's theory that primitive humans lived in small groups or tribes dominated by a powerful male, and the rest of the men killed the alpha male out of desire, hate and jealousy, then felt guilty and created a totem or symbol to represent the alpha male, which later evolved into gods of religions
Freud's theory that the religious mystical experience ('oceanic feeling') is the desire (wish-fulfilment) found in every human being to return to the womb (in utero) to a sense of 'oneness' or 'connectedness'
Freud's theory that religion is a 'universal obsessional neurosis' because religious activities bear a striking resemblance to the activities of a neurotic person with Obsessive Compulsive Disorder (OCD)
as where fathers tend to be absent. These visions are also far more common among the celibate or unmarried. Therefore, supporting Freud's link that belief in God and religion is linked to a projected father figure.
It is now generally accepted that there was more variety in primitive societies than Freud suggests. For example, not all tribes had totems or even a dominate alpha-male.
Freud's Oedipus complex concludes why god is seen as male, such as Christian God. However, it does not explain/ignores why some religions have important female gods, such as Hinduism or the Egyptian Isis cult and religions which do not have a God at all, such as Buddhism.
Many ideas within Christianity are both unsettling and challenging. Following Jesus can be very uncomforting because we have to accept the belief that you and I are dirty, rotten sinners who need to take up our crosses, denying our own egos by allowing Jesus to be the helm of our daily lives.