“Whenever we are told to hate our brothers ...” When do you think this happens? Why? Who ‘tells’ us? Should we do as we are told at such times? What does the poet say?

It happens when some short-sighted political leader or hater of humanity wants to inflict war on the innocent people of a country.
 There could be many reasons behind this war such as religious fanaticism, greed to acquire land, or to take revenge of a past defeat, etc.
We should not accept anyone's ideology. We should judge people according to our understanding based on truth and righteousness.
The poet advises us not to hate our fellow brothers and sisters living in any country. According to the poet, they are people like us and share so many things with us. According to him, when we hate them or take up arms against them, we harm our selves.

What the poet means dear, is that you ought to hate your brothers when you find them wrong, and despite your explaining satisfactorily how they are wrong, they choose to act in a manner more selfish. What's wrong and what's right depends upon your basic instinct besides religion and law. A simple test is judging the way; you would decide an act if it happened to you. Know this that you wouldn't sin if you act as per what you believe is right, as kids are not publishable in our country. But understand that what's right depends upon a person's belief and not what the majority believe. Hope you know what I am trying to convey...!

Whenever there is a war, Leaders tell people to hate the other country. They tell us to do so because of their personal gains. But we should not act as a puppet in their hands and do as they say. We should understand that War is futile and analyze the situation before jumping into conclusions. The Poet says that if we fight against them, we kill and condemn ourselves.

It happens when some short-sighted political leader or hater of humanity wants to inflict war on the innocent people of a country.
 There could be many reasons behind this war such as religious fanaticism, greed to acquire land, or to take revenge of a past defeat, etc.
Biased leaders might impose their ideologies on the people of their country and appeal them to hate the people of an enemy country.  
We should not accept anyone's ideology. We should judge people according to our understanding based on truth and righteousness.