Ang point man gud sa Roman Catholics citing Mary as Immaculate (spotless) and remaining a virgin for the rest of her life is to promote her as the "Queen of Heaven" which we also need to worship aside from Jesus Christ. That's why protestants argued coz we can never read this teaching from god's word.
In reality, Mary herself needs God and Saviour coz she was a mere human.
Luke 1:
46 And Mary said, My soul doth magnify the Lord, 47 And my spirit hath rejoiced in God my Saviour.