SPRINGFIELD — Barack Obama decried “the smallness of our politics” when he launched his historic presidential bid from Springfield back in February 2007.Exactly nine years later, he returned to the capital city with much the same message.“We can’t move forward if all we do is tear each other down, and the political incentives too often today reward that behavior,” Obama told his former colleagues in the Illinois General Assembly.In a rare homecoming, the former state and U.S. senator …