Sharing in the beatific vision of God does not take away our free will, but it makes the distinction between good and evil so abundantly clear that no rational intelligent being could choose evil. It is like being offered a choice between a bath in warm water or boiling acid. We COULD choose the acid, but no rational person ever WOULD.
Well, what about the angels at the very beginning?
Just to clarify - angles are created beings, just as we are. There was a “time” when angels did not exist, but God brought them into existence. Angels are not eternal.
They lived in the Divine presence continually yet some strayed and fought against Him.
We also live continually in the Divine presence, but we are unable to fully perceive it.
Although the Catholic Church has no doctrinal position in this regard, most (if not all) theologians agree that the angles also did not initially perceive the full glory of God and did not initially share fully in the beatific vision. Therefore the angels were created and given only a limited perception of God. Some accepted God and others did not.
One thing that differentiates angles from humans (according to many theologians) is that angels have perfect free will. Thus, when they make a free-will decision, the decision is final and cannot ever change. Humans have imperfect free will - we can decide one thing today and another thing tomorrow. So if we make a bad decision today, there is hope that we will reverse it tomorrow. But angels commit themselves perfectly and completely to their decision and cannot ever change. This is why (many theologians believe) that Satan can never repent.