Fundamentalism and syntheticism and practical implications

Hello,
I read your book “Truth and Unstable” and from the beginning I felt disgusted by the utilitarian striving to create a system of thinking that would not lead us to extreme consequences.
But my main problem with the book’s conclusion in favor of synthetic thinking is that it doesn’t solve the problem at all.
Because the holder of the (unstable) synthetic truth has no problem using radical tools like the death penalty or Southern law or eliminating a terrorist like a cat, etc.
At first I thought about the difference between killing out of a lack of respect for the lives of certain people and killing as a possible tool, but that doesn’t hold water.
In short, a synthetic thinker, just like his fundamentalist friend, can decide (even with uncertainty) on total/extreme actions based on the truth he believes in, and the only thing a synthetic view does is lower the threshold of certainty, which in a utilitarian view (yikes…) can lead to the opposite situation of lowering values ​​even further.
I remembered a story about a man who wanted to kill a second man after he saw that he was coming to kill him, and a third man tried to convince him that maybe he didn’t see well, and that he couldn’t trust his own thoughts, etc., and the first man replied that he intended to murder the second man with the same vision and thought that he saw coming, so it’s offset.
In short, morality and values ​​stemming from a synthetic view cannot be stronger than extreme actions motivated by that view.
With joy and pleasure
Reuven