Ligue 1 - Dabo rages as Barton signs
Barton was handed a four-month suspended jail sentence in 2007 after assaulting Dabo during training.
"He is nasty, a traitor. Sometimes I get the impression we have rolled out the red carpet for him. I speak to remind people that Barton is a very violent player, far from the image he tries to portray since arriving at Marseille," Dabo told L'Equipe.
"We condemned Jeremy Menez, Samir Nasri and Yann M'Vila for little things and then the French media is very forgiving with someone who has committed horrible things, as recently as May. No one wanted him in England . . . that means there is probably a reason.
"(With our history) There was a trial, he pleaded guilty and accepted a four-month suspended sentence. When he speaks, he denies it, he said I initiated it. All the team members present during the assault testified in my favour.
"He says he is a man, a bad boy, but he is just a coward."