The premise is correct. God loves us. But His love is strong, rather than weak and permissive.
The question should actually be, "How can a holy God let sinful people into heaven?" You can’t simply camp out on God’s love and forget His holiness.
No one is worthy enough to enter heaven. But because of His love, God wants us to be with Him. So, Jesus’ death on the cross, where He paid the penalty for all that we have done wrong, was God’s way of satisfying His holiness and demonstrating His love.
Look at that sacrifice: God has done everything possible to keep people out of hell. What have you done about that provision? Are you choosing hell rather that heaven?Schaeffer deliberately misunderstands the point of this sort of question: just because you don't want bad people in Heaven does not mean that you have to send them to Hell. An alternative could be to reincarnate the bad people until they learn to be good... perhaps they can be rehabilitated in some other kind of afterlife? Surely a Good God would think to try these things? Thus the answer is begging the question.
However, the answer may reveal something of the kind of God Scaeffer believes in - for instance, he takes pains to redefine the question so it no longer relies on God's "goodness" ... perhaps Schaeffer does not really believe in an all-good God? Instead he prefers one that is loving and holy. This certainly removes most of the usual objections.