It is perhaps a semantic point, but I consider a && !a objectively false and a || !a objectively true -- but even there, you have to accept certain axioms of logic. And I consider initiating violence against a peaceful person objectively immoral -- but if you don't already accept that, I'm not sure how I could convince you.
I respectfully disagree. a && !a is not objectively false, and neither is a && !a objectively true. You are correct within a set of accepted axioms, defined by Mr. Boole. You might be incorrect within another set of axioms.
That's exactly what this thread is about : when you do real maths you always start from definitions and axioms. It's not objective or subjective, it's well defined.
I do prefer to read opinions of people who state their axioms first, rather than people who pretend to be objective.
Initiating violence against a peaceful person is immoral in lots of cultures (including mine). Your culture is your set of axioms here.
For such a thing to exist an entity with no desires, interests or stakes would have to make this objective judgment.
All we can do is perhaps identify the different subjective components in a argument.