The real reason why we hate disagreements is because we have the illusion of rationality. If you disagree, you are wrong and I can prove it!
OK, I am just kidding, let me try again.

Sometimes I feel hurt by other people disagreeing with my views and opinions because it sounds like they are against me.
Does it make sense to you? Do you feel the same?

Red is my preferred color. I like red. I like to communicate my preference to my friends, because I feel it is part of who I am, it is “me”. So if someone fails to get interested in my feelings towards red (I can talk endlessly about the energizing effect that the red color has on me!) or, worse, “disagrees” with me by immediately interjecting something like “oh, but red is such an aggressive color, blue is better at communicating bright and cool energy!” I might feel discounted or even personally attacked.

Of course, a tactful person might first validate my feelings by saying something like “I see how red has a positive effect on you”, before adding “ myself, on the other side, I react differently than you to colors, it is blue that gives me energy”.

It is almost as if I need to be reassured that it is OK to have the feelings I have towards the color red, before I can unlock my curiosity about how others can perceive colors, open the door to learning that also another color can convey the sensation of energy, unleash my fantasy to imagine all the many ways colors can be perceived in ways I alone can never imagine, and allow my heart to joyfully accept and genuinely respect a surprisingly different point of view.

Once I stop protecting and defending myself (actually my self image) I can open all my senses to the full excitement of learning interactions and constructive disagreements.

Before you discount my example as silly, think about how many times in our daily lives we feel irritated, attacked or discounted by the simple lack of validation, much more than by the fact that others have different perceptions, opinions, judgment, etc.

Why does it happen?

Well, we only start to learn about our brain and we will never learn it all of course (“if the human brain were so simple that we could understand it, we would be so simple that we couldn’t” goes a famous quote), yet we start to realize that our brain tends to take short cuts to save energy: our brain quickly forms an opinion about just about anything, and only then gets busy to find rational proof, often stopping at “enough evidence”. Thus when we insist on using rational logic to “convince” others, we are simply showing our own path that justifies our own first impression; when the other party tells “I understand”, and still goes a different way, it is clear that the issue is not in the logic that supports our opinion (and there is no point in adding facts over facts) because a different and yet equally valid logic could justify a different opinion. Unless we are ready to disclose our “opinion” with humble curiosity, without raising it to the status of “universal truth” we are probably still irrationally going to war to rationally try and decide between red or blue impressions. The alternative is of course to open the dialogue and learn together.