Trent Session 6:
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CHAPTER VI.
The manner of Preparation.
See where it says "Preparation"? In order to properly receive the Sacrament, it's necessary to have repented of your past sins. This is a prerequisite for being justified in the Sacrament, but it's the Sacrament itself that blots out all sin, original and actual, as well as all temporal punishment due to sin,
ex opere operato. If someone were still intent upon continuing in grave sin, then they would not be justified even when receiving the Sacrament. But if they have the proper dispositions, then the initial justification conferred in Baptism wipes away all sin. Similarly, if someone had no natural faith in the Church or if someone did not intend to receive the Sacrament, they would receive the character but no justification. Let's say I just walked by and randomly baptized some infidel. I would commit a sacrilege since the individual would receive the Baptismal character, but no justification due to lack of proper dispositions. But IF they were justified in Baptism or in their initial justification, they are reborn.
Initial Justification = Rebirth
Rebirth (as the term inherently suggests) = a total cleansing of anything that would prevent entry into Heaven (including temporal punishment due to past sins)
It couldn't get simpler than that.
You've effectively denying Our Lord's teaching that no one can enter the Kingdom of Heaven without being "born again" (and Trent defines the term "born again" very clearly).