The problem is, the trolls would not just post in RESPONSE to a discussion. They would START the discussion -- and then kick off and suspend everybody and anybody that disagreed with them. You give them the power, they WILL abuse it. They do that now, here on YA. So, no, the controls you suggest...
On the bottom of the page is a tiny link: "Tell us what you think". Go there, click that -- and tell them what you think. If enough folks do it, maybe they will listen.