I once thought this, and I disagree.

There are many issues which you can find common ground for a base case of moral absolutism when you are not being absurd.

Moral relativism allows you to accept the actual evil of other's actions as a product of their culture.

That is the kind of thinking that allows people to say genital mutilation is a cultural thing.

Claiming moral absolutism is the root of all evil is a morally absolute statement in itself. What is the basis for this claim?

RMS is absolutist, does that make the FSF evil? If one is absolutist about being against rape or child crimes, what evil does that cause? The courage and consistency of ones conviction shouldn't be the basis of judging its merit.

Can we start the counter of americans that do nothing against the killings of black people or americans/europeans that don't care about their government killing hundreds of thousands and displacing millions? Moral relativism.

I don't actually have a strong opinion on the matter, but keep in mind the OP is advocating killing people to improve the state of the country. In the abstract. It's "kill the narcos", not "if a narco rackets or threaten me", then I'd be justified in taking him out".

For me that's quite a line to cross.

Start fighting using non-violent means and maybe only resort to violence when confronted with violence from the other party.