The England wing was handed the suspension by an RFU disciplinary panel on Tuesday and is set to miss two Heineken Cup matches over the next two weekends, plus two Aviva Premiership games over the festive period.
Ashton was disciplined for hauling Alesana Tuilagi into touch by the Leicester player's hair, sparking a mass braul after which two men were sent off.
But Mallinder told Sky Sports News: "We think that four weeks is fairly harsh. Of course we don't want these incidents to happen but it was actually an isolated incident and I don't know if that would be a red card or not in a normal game.
"It wasn't a normal game - it was a big, physical encounter between two rivals and a fantastic game of rugby. It was just a shame that something like this had to happen."
Northampton have until Friday to appeal against the ban.
Meanwhile, Mallinder has reiterated his interest in replacing Martin Johnson as England manager, although he admits he is in no rush to leave Saints.
He said: "I have got a fantastic job here. Northampton Saints is a fantastic rugby club. I love it here and I have got lots of support from the board and from the owner and from all the supporters who attend. So I am very, very happy with what I do here.
"I have said in the past that at one stage I would love to coach England and I still mean that. But I am 45 years of age, I have got a lot of time to go and it has to be the right opportunity for me to make that next step."
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