Agreed with fofa. The sentence is about renouncing hate. What a nice elaboration by "Benjamin Spock", Humans can be the most affectionate and altruistic of creatures, yet they're potentially more vicious than any other. They are the only ones who can be persuaded to hate millions of their own kind whom they have never seen and to kill as many as they can lay their hands on in the name of their tribe or their God.

'I have decided to stick with love. Hate is too great a burden to bear.' This is Martin Luther King Jr's quote in which he talks about one of his principles that he always stuck to: It is love as opposed to hate. 'Stick with something' means 'to continue with something or continue doing something'. He always believed in the power and influence of love. That's why he decided to follow the same principle so that he can avoid the bad / destructive effects of hate.

a wise man really he means that he tried" hate" before found no use of it, maybe it caused him problems, so, he decided to love and this love will give him the power to face and solve any problem this is what i think