The Sinn Fein president was questioned for four days at Antrim police station by detectives investigating the 1972 murder of Belfast mother-of-10 Jean McConville.
Police Service of Northern Ireland (PSNI) chief Matt Baggott said it would have been wrong to treat Mr Adams any differently from anybody else.
Sinn Fein has claimed there is a "dark side" opposed to the peace process within the police force and blamed an embittered rump left over from far-reaching reforms for their leader's detention.
Mr Baggott said: "Questioning the motivation or impartiality of police officers tasked with investigating serious crime in this very public, generalised and vague manner is both unfair and inappropriate."
His remarks came as Stormont First Minister Peter Robinson said his Democratic Unionist Party (DUP) had been on the verge of putting a motion before the power-sharing Assembly calling for Sinn Fein's exclusion from the ruling Executive.
It was considered following comments made by senior republicans, including Deputy First Minister Martin McGuinness, that they might review their support for the police if their leader was charged.
Mr Robinson said he stopped short of the move when Sinn Fein "corrected" its position, a reference to Mr Adams' statement of support for the PSNI upon his release from custody on Sunday.