The Balfour Declaration was a “unilateral move’ by the British cabinet in the face of the crumbling Ottoman Empire. I suspect that deep down if not openly this is castigated as imperialist by the left wing.
Of course it was imperialist. That was a time of imperialism, and the British Empire was rewarding its Jewish allies, Chaim Weitzman, The Jewish Brigades, etc., by awarding them a homeland under British protection, for their substantial help in taking apart the Ottoman Empire. Unfortunately, a clique of pan-Arabists within the military and the British Foreign Office began undermining the Balfour Declaration almost the moment that the League of Nations ratified it.
I could argue that Russia’s presence in Syria is imperialist, too, and it is. But somehow it’s only immoral when Britain or America does it. China can do no wrong, and Russia can only do wrong after they renounce Communism, and even then only sometimes.