Taking the "high road"

My current employer is looking at beginning talks with my former hell employer about a partnership for a project to benefit employees. I've been trying to stay out of these conversations because just because I hate my former employer doesn't mean I should make those that work for them suffer. The project would be good for the revenue of my former employer. But as I've thought more and more about it, I'm not taking the high road. I'm doing my current employer a disservice by not being honest about my former employer. To wit, I genuinely feel that the upper management team is not proactive in dealing with problems that arise. They let bad things slide for far too long because they are so focused on their expansion that they can't fix the issues currently in the organization. Their employees are not motivated by anything other than fear. Their expansion appears to be unfocused and they end up with offices they don't know what to do with. And a quick google search tells me that their CFO, the one person I thought was reasonable on the executive team, is gone. Big shocker. It won't be up to me whether we do this partnership. If I had that power, I'd totally go with another group who is larger. But I'm definitely going to bring my concerns to the table.