Because, once it was exposed that Turino and Hall had a questionable background, Vinny became their saving grace. It appears he was just a figurehead to forward their scam against their investors. They attempted to use Roy Lerman in much the same way.
Of course allan should be threatening to sue them instead. Of course it is also possible, they have had(or do have) a working relationship together, and allan wouldn't want to be exposed. I can't confirm, but I've heard rumors in the past that slurpy was given shares to shut up, by Turino. All just my opinion, of course.