Redknapp dismissed the notion United broke a tradition of giving their managers time to succeed, as they did with predecessor Sir Alex Ferguson.
Harry said: "Sorry to see David Moyes to go so quickly. He needed a summer to build his own team. It was a bit of an ageing team, or a team that needed a bit of surgery if you like, so it was a shame.
"Man U are not a sacking club because they had a manager who was there 20 odd years.
"If they'd had a manager who was losing every week, they'd have sacked as many managers as anybody else."