You will also note ( by reading beyond the first sentence) that there is scriptural proof.
Please remember that Catholics are not naïve enough to believe in the man made myth of Sola Scriptura.
The salutation of the angel Gabriel -- chaire kecharitomene , Hail, full of grace ( Luke 1:28 ) indicates a unique abundance of grace, a supernatural, godlike state of soul (these comments are mine: that catholics believe this is scary and explains a lot of the basis for their elevation of Mary to what she is not accorded in the Word), which finds its explanation only in the Immaculate Conception of Mary. But the term kecharitomene (full of grace ) serves only as an illustration, not as a proof of the dogma.
(The Vulgate has mistranslated the passage in Luke 1:28 regarding "full of grace". The major translations agree on this. Comments mine)
From the texts Proverbs 8 and Ecclesiasticus 24 (which exalt the Wisdom of God and which in the liturgy are applied to Mary, the most beautiful work of God's Wisdom), or from the Canticle of Canticles ( 4:7 , "Thou art all fair, O my love, and there is not a spot in thee"), no theological conclusion can be drawn. These passages, applied to the Mother of God , may be readily understood by those who know the privilege of Mary, but do not avail to prove the doctrine dogmatically, and are therefore omitted from the Constitution "Ineffabilis Deus".
You've got nothing from the Word to substantiate the catholic claim on this.
Hell no!
They 'believe' apparitions and visions and magisterium decisions instead!