It's a complicated situation. The Taliban make up a good portion of the population in Afghanistan. You can't just marginalize them, ignore them, or expect them to realize they are wrong and give up. Their struggle is a religious one and they're not going away any time soon. Haqqani Network are closely allied with the Taliban as well, but they have been known to fight each other for local power. Beyond that, al-Qaida is a worldwide Islamic terrorist organization that is loosely connected with both. On the GIRoA side, (Government of the Islamic Republic of Afghanistan), Hamid Karzai has been affiliated with organized crime and has pardoned known criminals immediately after their arrest. The Afghan parliament itself is known to house a number of Taliban associates and have also interfered with arrests and the judicial process. Afghanistan is saturated with corrupted officials and warlords. A messy withdrawal is what the U.S. wants to avoid. Negotiations with all players, secret or not, is probably the best thing that the US can do.
"Pakistan's not the only one double-dealing " Right, and as your quote shows, the U.S. is #1 at it. For exposing U.S. double-dealing on Wikileaks, Bradley Manning has now been charged with "aiding the enemy" and many other charges, and will be sentenced to life imprisonment.
WHAT OUR CHILDREN ARE DYING FOR IN AFGHANISTAN... The Taliban had all but eradicated the opium growers before the US invasion. So why is cheap Afghani heroin flooding into the United States? In Afghan fields the poppies grow. Between the crosses. Row on row.