I think that it's the old fight or flight response in people's heads. Whenever someone with a different opinion comes round, instead off looking at what they sat rationally, they have an instinctual reaction in their brain which was evolutionarily evolved to protect them against threats (which makes you really think about how many times our ancestors must have been attacked by lions or warring nations that it must be so baked into our genetics). It's because of this programming that prevents humans from living peacefully, and yet degraded imbeciles prop up these things as virtues. It reminds of the fact that all humans are apes, and the degree of which a little burning in the amygdala incites their praise or mockery determines the entirety of our civilized endeavors. When did someone take the advice of Kant, and block out these earthly passions of praise or scorn begot of empirical biological determinism, in favor of the end in itself; the categorical imperative? Or Spinoza, who said how he labored not to scorn, but to understand? Pascal's wager. They don't wager it in favor of all encompassing biological determinism. What do they have to lose?
Of course, in a wager there's a bet. For them they must believe in free will because it gets them a ticket to heaven, in their reality, which requires a free will framework. For if we do not control our actions, and god truly punishes you, then he set you out on an assembly line to commit whatever sin you did and then you fall off the assembly into a fire of burning hell. But I thought no one but catholics believed in hell? Apparently not, there is apparently enough people who buy into the ideology of believing in hell, likely by force of societal pressure, who will display a speciously inexplicable aversion to the idea that we do not command our bodies, which is in fact nothing more than the excitement of the amygdala invoking a praise or scorn arbitrarily evoked by genetic predisposition.
Because this is genetics people will obviously think that our begotten condition is a result of incontrovertibly good natural processes. This is also the same argument used to condemn lgbt people, because it's not "natural". However, that proposition can be demolished by the simple fact that our same natural processes are responsible for wars, feuds, and all the things the bible says are sins like hatred, anger, jealousy, etc. The ultimate irony is all the so called "deadly sins" are just as much as natural and harmful as the supposedly unnatural. To a much greater extent is the natural more harmful than the unnatural. But this dichotomy is false, because there is not natural and unnatural, because everything is natural. Natural meaning occuring by the laws of physics and biology. If a person acts on biology to altar it, it is merely changing the path of matter in a way which is different. That is what it comes down to, is interminable differences. The differences are endless, in arrangements of our cells in infinitely complex patterns. There is no inherent good or bad, because everything is merely the playing out of cells.
This threatens mystical thinking. But it's these mystical thoughts, like good and bad, and morality, and religion, and politics which people impose on one another, and they play the game of playing a game of Pascal's Wager. In this game of chance that they play for a unintentionally catholic ideology, they dismiss the possibility that all feuds are for naught, and peace comes through the categorical imperative, which relies on the naive assumption that humans are inherently rational. Humans are inherently irrational, and therefore we will continue to impose unnecessary strife on each other. Like roman gladiators who tossed people in a ring to watch them fight. Human beings love violence.