Because James Kirkup was an English poet, his work is not grounded in Hinduism or Buddhism, but the point of view he is espousing here is somewhat close to Ahimsa, in that he is arguing that since all of us, whatever our nationalities, share common humanity, we should not attempt to harm each other. 

In this poem, he does not condemn the positive aspects of patriotism, of loving one's own country, but he does condemn the negative side, when love for one's own country because hatred for other countries. The poem argues that what we have in common with other people is far more significant that differences in culture and nationality. 

The mood combines melancholy concerning war and hatred with guarded optimism about the possibility of people rising above hatred.