If these groups are found to have committed fraud, their leaders should be punished, or at the least, their permission to register new voters should be denied.
As I understand it, these groups pay the layabouts who register new voters an amount per new voter registered. Obviously, these individuals have a real incentive to register as many names as they can find (whether legitimate or not), so they can make more money. The key is whether the sponsoring (and paying, courtesy of George Soros, the AFL-CIO and other likeminded groups) organizations encourage or even knowingly tolerate fraud. If so, they would seem to be as guilty as the layabout submitting the fraudulent registration.