I think it's because he believes a born again child of God can lose his salvation and have his Father throw them in hell.
....that thinking taints every post regarding works or obedience.
Don't leave out the important point. You posted an incomplete and inaccurate argument. It actually goes like this:
'A born again child of God can <STOP BELIEVING> and lose his salvation.'
No longer living for God is the sign you have stop believing and that you will not be saved when Jesus comes back.
You can believe that a believer can never stop believing and that's fine, but the Bible is very clear what will happen if you stop believing, whether you think they can really stop believing or not.
One of the truths that reconciles the 'once saved always saved' verses with the 'not once saved always saved' verses is this: Believers in whom the word is well planted, holding fast, and flourishing, they are the one's who persevere and don't fall away into unbelief. They are the fourth kind of soil Jesus talks about in the Parable of the Sower-Luke 8:15.
Jesus said it is the immature, shallow rooted believers who can have the word easily torn from their hearts through persecutions and troubles and who fall away into unbelief-Luke 8:13. That's why it is so important that we get out of the world and it's loves and fill ourselves up with Christ in earnest study and contemplation and focus on the word. If you don't, the word won't be deeply rooted and flourishing in you and it can be uprooted from your heart in unbelief in times of trouble and hardship.