Salim took to Twitter to express his displeasure over the alleged comment, saying, people should watch "Sultan" before making such nasty comments about his son.
"In a TV debate Salman was mentioned as old enough to be a grandfather over and over. I request them to watch #Sultan in a theatre. And wonder how could a man old enough to be a grandfather do this," the 80-year-old writer tweeted.
He further said that people should resist their "temptation" to hurt someone.
This is not the first time Salim has jumped to his 50-year-old son's rescue.
Last month when Salman courted controversy by comparing his condition during physically-draining shoots of "Sultan" to a raped woman's, though Salim called his son's statement wrong, he said people should stop forcing Salman to apologise.
Salman is yet to comment on the statement despite repeated demands from various sections for an apology.