Government continuing to play favorites, helping out some companies at the expense of others

Why should the government subsidize businesses? All these subsidies of course help one firm versus another, though this is a more concrete example. From the Politico:

Turning up the heat on Boeing Co., Sen. Tom Coburn wants Congress to bar the Export-Import Bank from financing aircraft sales to foreign airlines if the transactions do “substantial injury” to American carriers competing for the same international routes.
As drafted now, Coburn’s legislative language appears to stop short of a strict, “shall not” prohibition. But he specifically targets “long-range aircraft” akin to Boeing’s new 787 Dreamliner, which is heavily dependent on international sales supported by Ex-Im loan guarantees. . . .