If you don't believe that your value system binds anyone else to behave in a certain way then how much does it really bind you to behave that way? Ethics and morality are either objective and universally binding or they're merely an arbitrary personal inclination that isn't even binding on those that have the inclination beyond legal or professional implications.
Ethics is hard. There's a reason it's not a solved problem.
Why is generally not wanting to hurt people a "reasonable foundational belief?" It's definitely not universal in humanity right now let alone historically just look at the celebrations of war crimes in Russia. Everyone who thinks there are binding ethical beliefs in any way must ascribe it to others otherwise they're just talking about personal taste and we don't need words like "ethics" or "morals."
Unfortunately this point doesn't prove/refute any point about morality.
Because most of the russians pro-war idiots (including most propaganda producers) sincerely believe propaganda and from their moral perspective they really are doing good by fighting Ukranian war criminals.