Down the millennia Buddha, Christ, Muhammad et al couldn't establish lasting peace in the world. Ashoka's and other examples of sporadic peace are nothing but blips on the sand of time. Everything is governed by the absolute law of impermanence. So wishing for permanent universal peace will, as always, remain a 'wish' -- ever beckoning to be fulfilled in some uncertain future, which will never be attained. Don't think it verges on pessimism; rather it's a sincere admission of stark realism.