He doesn't live in the real world, his head cannon is an awful fantasy.
I don't know how to say this in few words, but even in divided society individuals should be able to consider individuals on the opposite end as potentially simply misguided, or manipulated into opposite ideology, or simply misinformed and people should perceive their opponents as redeemable under some circumstances (rational or irrational) by some intervention, by enlightening them etc.
We can usually imagine our enemies having a "coming to Jesus moment" under some conditions. I mean we can literally imagine it happening as a possibility - not that it happens a lot or often. In fact it rarely happens but this ability to imagine them figuring their shit out is what stops us from cutting each other's throats most days. And Destiny doesn't seem to have that human trait alive.
For me personally the only people I am totally unable to imagine changing are seniors, and I mean 75+ seniors.
Destiny thinking every bystander is equally worth killing (as opposed to winning them over) actually means that his belief is that half of the population is not simply corrupt, it is intrinsically evil. They were born as "others", the entirety of humanity is split along the Trump line and that's enough to define the entirety of person. If mother of 3 kids gets killed it's fine if she was a trump voter, and the loss of a mother is disregarded as less than collateral damage, in fact she wasn't considered to be a mother 'cos her vote is the entire person. This is bizarre thinking, and he should spend more hours in therapy than streaming.
And I edit to add the bugging question: what about Trump winning is bad for Destiny? Not just bad but bad enough that no amount of human lives lost in preventing Trump win is too much. Does anyone have a clue what horrible fate awaits Destiny if Trump returns to White House?