At a news conference in Zagreb, Banac read out a HHO statement in response to Mesic's speech at Sunday's commemoration of the 64th anniversary of the 1945 break-out of dozens of last inmates from the Jasenovac concentration camp.
The HHO statement says that the European resolution on totalitarianism obviously has not yet come to Croatia "or how one can explain the fury of the opening remarks by President Mesic and other speakers."
The HHO says that "for more than three years President Mesic has been downplaying crimes committed by the Yugoslav Communist regime and trying to create convincing alibis for Tito's dictatorship."
Stressing that Jasenovac must not be used for scoring political points, Banac said Mesic's speech was inappropriate for the memorial site of Jasenovac and accused him of using the place to spread political propaganda.
The HHO statement reads that in recent days Mesic has said many untruths about HHO vice-president Ivan Zvonimir Cicak and reminds Mesic that "he knows very well" that HHO members are neither "false human rights champions" nor "history revisionists".
The HHO says that its members cannot be indifferent to Mesic's attempts to ensure that Communist crimes sink into oblivion, because those crimes had caused suffering, tears and evils to the same extent as those committed by the Ustasha fascist regime.
The HHO criticised Mesic for saying that the Tito-led regime was not criminal although it failed to prevent crimes.
The HHO also says that it will defend "the right to remember all victims, without exception, of all totalitarian, undemocratic and authoritarian regimes".
The resolution cited by the HHO was adopted by the European Parliament on 2 April. It expresses respect for all victims of totalitarian and undemocratic regimes in Europe.
"Parliament underlines the importance of keeping the memories of the past alive, because there can be no reconciliation without truth and remembrance and reconfirms its united stand against all totalitarian rule from whatever ideological background," the resolution says.
The resolution warns, among other things, that Europe will not be united unless it is able to form a common view of its history, recognises Nazism, Stalinism and fascist and Communist regimes as a common legacy and brings about an honest and thorough debate on their crimes in the past century.
Asked by reporters to comment on the HHO leaders' response to his speech in Jasenovac, President Mesic said later on Tuesday that was not going to comment on Banac and Cicak.