Her father protects (her) in childhood, her husband protects (her) in youth, and her sons protect (her) in old age; a woman is never fit for independence. (Manusmriti 9.3)
Ans. Protection doesn't mean supression. Don't try to juggle words. I don't have to explain the duties of women to perform and also dont restrict yourself to only one para or so. If you read Manusmriti fully and properly then you yourself will find the answer why he has written like this.
Thanks.