He’s essentially abandoning the fact that Christ is the only savior and positing a sort of di-theism. There’s only one God and only one heaven. All who are there will have to deal with the reality that God is a Trinity and Jesus is, in fact, God the Son. Jews and Christians will not have separate heavens and separate Gods. It is no sin to say this: it is simply an affirmation of the most basic teaching of Christianity: that all who are saved are saved by Christ. It only becomes sinful when a Christian attempts to compel a non-Christian to agree with him. Christians don’t need to do this. If their doctrine is true, “every knee shall bow” to the truth of it in God’s own sweet time. Our task is to bear witness to Jesus as Lord, to propose, not impose, as JPII says. It is not to give noogies to those who do not agree with us until they cry uncle. But neither is it to abandon the basics of our faith out of a false notion that this is somehow affirming non-Christians in their okayness. Both Jews *and* Christians are bound to obey their consciences.