Here is the rhetorical knock-down punch, the ultima ratio, of the Forced Birther.
“What if your mother had chosen to abort you?”
Good for me that I have a reply ready.
“I regret that she didn’t.”
By the values inculcated in me by that same mother, it would be rotten of me to savor the look of confusion and disgust such a retort would occasion, but I cannot guarantee that I would not do so.