HARRY
I need to protect him—

DRACO
My father thought he was protecting me. Most of the time. I think you have to make a choice – at a certain point – of the man you want to be. And I tell you that at that time you need a parent or a friend. And if you’ve learnt to hate your parent by then and you have no friends... then you’re all alone. And being alone – that’s so hard. I was alone. And it sent me to a truly dark place. For a long time. Tom Riddle was also a lonely child. You may not understand that Harry, but I do – and I think Ginny does too.

GINNY
He’s right.

Harry Potter and the Cursed Child - Chapter 2 :
See this quote in the Pensive -