First, the side of town doesn't matter. The team actually studied the issue before allowing the location. And remember, they wanted it in Tempe, but hair on fire idiots from the Phoenix City Council yelled "people will die!" and it didn't happen. Fact of the matter is, the number of people who won't come because of location are offset by the equally small number of people who will come because of location.
Second, as a transplant myself (grew up in Dallas rabidly supporting the Cowboys), I see it as a matter of community. When people insist on supporting the team from where they used to live, they're just using that as an excuse to not have to follow a team that loses more than it wins. They didn't like Chicago enough to keep living there? Fine. Support your new home. Or go back to Chicago.