Because love is the only way forward. And I don't say that out of altruism. Hatred will consume and embitter a person.
There are people who have suffered far greater injustices than being bullied in school and were resilient enough to maintain a generally positive disposition that serves them well. There are also privileged individuals who never faced anything most people would consider a real problem and yet are extremely cynical and bitter at the world as they see it.
Setting all judgement aside, what is the better way to live solely for oneself?