Thank you for asking for me.
Unless you, or someone else told him how infuriated you were at the exchange, and why, he would have no reason to know---nor to deny leaving your son on the sidewalk.
He may be trying to document the facts differently than you reported so he can use his denial as evidence if his behavior becomes an issue in a custody matter. Or he could simply be trying to control you---trying to make you second guess yourself. This a fairly typical game played by people with power and control issues.
The best thing that you can do is to minimize contact with him, don't exchange emails with him, and respond to calls only as regards XXXXX XXXXX avoid conversations which are argumentative in the least. This may make him frustrated as he takes power from trying to control you and manipulate you---so be aware of that and don;t fall into his trap of argument, anger and hate.
I wish you the best in 2011.
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