Wow,  what a statement. And so insistent.  And so wrong.  The human heart is full of love - until it's abused and brutalised by others who are damaged.
Have you ever seen a mother beating and eating her newborn?  Apart from those who are mentally ill or damaged?

Most mothers love and cherish their offspring - it's the most basic instinct of all. And from that basis develops love for others until mistakes and circumstances affect the outcome.   it's not a struggle to be good.  It's a strain to be bad - that's why people suffer when they are abusers.