We aren't making that argument. It is the fact that we have disparate laws in neighboring jurisdictions that is the issue in re: Chicago and gun control. Perhaps you haven't been following the actual discussion, instead relying on your own magic thoughts instead.
As long as Indiana has different laws...and as long as Indiana borders Chicago...then the gun control considerations simply cannot be thought of as Chicago's alone.
Then of course the reality of the situation. First, homicides in Chicago are DOWN from their all time highs. Second, the issue is gangs. Chicago has a bad gang problem. They deal drugs...and of course, cons don't want to legalize drugs, so they prefer to keep the profits and the control of these substances in the hands of the gangs.