Not to denigrate your defense of the film, but making us look as disgusting as him is the purpose of his trolling. He isn't trying to make you feel a little bad, he's trying to get a response. The best way to respond is to pretend you have no idea why he would say those disgusting things, and say off-handed condescending insults like "some people's kids..." or things to turn their attack around, like "look at the types of people that are against the truth" and "I guess bad people will attack when you do good".
I am a master of insult. A quality I have (although I am not proud of it) developed due to the studying of the masters of the art.
If someone insults me, or my family, they will receive the most blistering insults in response. If they persist I will reply with some more, and then just ignore them.
That usually disturbs them enough that they are disinclined to try again.