In an interview with Du Nord, Chicago Red Stars GM Peter Wilt sums it up perfectly:
The two most important audiences in American soccer are suburban families, which are traditionally conservative and sensitive to vulgarities and rowdy behavior, and young, urban, male, passionate fans who like and partake in extreme behavior. It’s two extremes that are oftentimes seated side by side. It’s ironic that they have this dichotomy while their end goal is the same: supporting the team they love to victory.
The challenge for MLS and our other domestic leagues has never been the so-called Mainstream Sports Fan. This mythical beast is not relevant to football’s medium-term success, any more than Tom Delay is relevant to current US foreign policy. The challenge, now and for the foreseeable future, is to establish credibility with all the American soccer fans who already exist.