Qwert, i agree that most hold that if a jew is killed because they’re a jew then they’re considered to have been killed al kiddush Hashem. Rav Miller didn’t dispute that in itself, but rather said that they don’t get rewarded for it “besides suffering a little less in gehinnom” if they were apikorsim/frei b’mayzid, even in the Holocaust. This was a controversial opinion.
But this has no bearing on meir kahana. He wasn’t killed because he was a Jew. He was killed because he declared war on the Arabs. They killed him because he was a threat to them. Did they hate jews? Most likely, yes. But the assassination was not due to him being jewish or even due to representing with or being associated with the so called jewish state. It was because he wanted to expel all arabs from israel, by force if necessary.