Disciplining doesn't mean hitting.
It's root word is disciple which means "to teach"
We teach our children every day.
We teach them to follow our directions or we help them.
We teach them how to be kind to each other and love each other without hitting them to teach them.
I don't hit my kids when they're learning to walk, I don't need to hit them while I'm teaching them how to act.
My NIV says for verse 6:
because the Lord disciplines the one he loves,
and he chastens everyone he accepts as his son.
Chastens is VASTLY different from punish. Chasten according to my Oxford dictionary says: to have a restraining or moderating effect on.