Consumer activist: By allowing major airlines to abandon, as they promptly did, all but their most profitable routes, the government's decision to cease regulation of the airline industry has worked to the disadvantage of everyone who lacks access to a large metropolitan airport.
Conclusion (has worked to the disadvantage)
The government’s decision to cease regulation has hurt everyone who lacks convenient access to a large metropolitan airport.
Evidence
After deregulation, major airlines quickly abandoned all but their most profitable routes.
The consumer activist argues that this abandonment has disadvantaged those without access to a large metropolitan airport.
Evaluate
The consumer activist’s argument is a causal one: he contends that deregulation led major airlines to drop less-profitable routes, thereby harming consumers in remote areas. In order to claim this, the activist must assume that major airlines flew those less-profitable routes despite their low profitability because government regulation required or encouraged them to do so.
In other words, his argument depends on the assumption that the government’s regulation played a key role in sustaining the unprofitable routes—and with deregulation, the airlines felt free to drop these routes.
Goal
Look for an answer that supplies the missing link: it must assume that before deregulation, major airlines were compelled, at least in part, by government requirements to continue operating less-profitable routes. Without this assumption, deregulation would not necessarily account for the subsequent loss of service in areas distant from major airports.