Everyone is at fault
The government shouldn't have allowed this.
The GPS industry should have lobbied against this before Lighsquared got its permits.
Lightsuared should have known it would interfere with GPS.
GPS is far more ubiquitous than LTE. The world already depends on GPS, they don't depend on LTE. So GPS should have precedence where a conflict is discovered.
If the government fucked up, then it should give Lightsquared another frequency to play with.