That would make Jesus a liar. And as the bible goes, there are better motives to move people to live a moral life. Believe it or not, the Christian motive to moral living is to know that Jesus fulfilled it for us. That is one argument I fine to be convincing, that is there are so many apparent contradictions (odd as that may sound). Take the given example here. The motivation to live a holy life is to know that Jesus is our holy life for us. Jesus has already given us righteousness, therefore go and live righteously.
But you see, if what you want to do is to say, here is the whip on your back, go and do it or else. That only lead to disparaging sadness. If we say, it is done already, and go and live in sin as you were (As I think Anom ends up holding to), then that promotes evil. But Jesus died for the guilt of your sins, and lived a perfect life of righteousness for you--in your place. The whip is removed, and guilt is off my back; therefore it gives me motivation to live a righteous life to thank God for all that he as done for me. Grace becomes the motivation, and love moves us to acts of good works; NOT works to earn Heaven; and also NOT fear that drives us to avoidance of Hell.
Do you see the counter intuitive? There are so many more like it.
But I could almost bet you, when you talk with atheist, the other two is what they have in mind, and not grace.
"... but doesn't actually have the heart to send anyone to eternal torment?"
God is a HOLY God. God would be unjust if he were to let anyone into his Heaven who are sinners against his Majesty. Every sin is a sin against God. Everyone crime is against God's higher law. God would be unjust and un-good to let sinners enter his Heaven, without those sins punished for. We do NOT let a judge to say, "So, you are found guilty of child abduction, molestation, rape and murder, but I am feeling good today. I will let you go with a warning." IF God is holy that means pure from sins, and good that means that he would do what is just, then God would have to punish sin.
"If God only told us what we needed to hear, how would we know? Don't parents do that all the time?"
And again, God would be a liar. In actuality, that is what atheist would like isn't it? A god who would just tell them what they want to hear. Like a parrot that is trained to say "Yu ar beeeuiti-ful." But that is hardly the God of the Bible. God tells us what we need to hear. That is love isn't it? "Don't take that step, if you do, you will fall into a dark pit." It may not be safe to yell fire in a crowded room, but surely it is less safe to let everyone die without warning anyone about the fire. Love and pity requires us to tell the truth, and it is only the truth that sets anyone of us free.
That is what I think about what you wrote. I am sure you are able to see it, given the Christian point of view. I speak with atheist people on my blog because I am trying to tell them about the fire, and I am calling them to run from it. But what is more, I want to tell them about the Grace of God that is able to save them from their sins and make them right with God, if they would believe in Jesus and trust in him to make them right with God. Then and only then, can they find peace in life and in death, and motivation to live their life to the glory of God.