Peter says that He bought em, not they. They deny Him.
The guy from that link has good points.
www.evidenceunseen.com
But why would Christ pay for someone’s sins, if he knew that they would ultimately reject him? Why not just die for those he knew would receive the offer?
We aren’t certain on how we should answer this objection, but we feel that our biblical exegesis should inform our view of God’s actions and plan. To put this another way, our philosophical speculation should not trump God’s revelation. At the end of the day, we don’t know God’s plans and desires; we need to depend on his revelation to us to understand this. And God’s revelation makes it clear that Christ died for the whole world—not just the elect.
the doctrine of limited atonement has severe practical problems. For instance, we could never tell someone with certainty that Christ died for them under this view, because we are not sure. As counselor Jay Adams writes, “As a Reformed Christian, the writer believes that counselors must not tell any unsaved counselee that Christ died for him, for they cannot say that. No man knows except Christ himself who are his elect for whom he died.”[8] We feel that there is a major practical problem with this position, and we certainly never see this sort of approach in the NT (1 Cor. 15:3; Acts 3:26; Lk. 22:20-21). For these reasons, we hold that this doctrine should be abandoned.