This is an evasion. While theoretically possible to "thread the needle" such that two parties to a conflict are weakened while a third party is empowered, U.S. intervention in Syria will almost certainly empower either Assad or radical Sunni militias. There is no reason to believe we or anyone else is capable of pursuing a "third way." That level of precision is beyond what we're able to realistically exercise.

The Washington Post's coverage better captures that reality:

The breakaway al-Qaida group is the most powerful faction fighting Assad’s forces, which means a U.S. campaign to weaken the Islamic State extremists could actually strengthen a leader the White House has sought to push from office. Obama could try to counteract that awkward dynamic by also targeting Assad’s forces, though that could drag the U.S. into the bloody, complex conflict—something he has studiously tried to avoid.

The story then presents an evasion from the White House:

White House spokesman Josh Earnest said Monday that Obama has not made a decision on whether to take military action inside Syria, but noted that the president has demonstrated his willingness to take military action to protect American citizens. “That is true without regard to international borders,” he said. Earnest tried to tamp down the notion that strikes against the Islamic State could have the unintended consequence of bolstering the Syrian government, saying: “We’re not interested in trying to help the Assad regime.” However, he noted that there are “a lot of cross-pressures here in this situation.”

A White House committed to leveling with us about the war it may start would admit that attacking ISIS will help Assad whether that "interests them" or not, and argue that doing so is the least-awful option.

Is it, though? One reason hawks avoid acknowledging the implications of intervening in Syria is that doing so strengthens the case for non-intervention. As Daniel Larison puts it, "Fighting wars of choice is bad enough, but it is simply perverse to insist on making deals with ugly regimes in order to facilitate the war of choice. If the most effective way of fighting ISIS requires the U.S. to go to war in Syria in concert with the Syrian government, that is just one more argument against waging a war on ISIS in the first place."

A related evasion is the tendency of hawks to undersell how long a war would take and its cost. After the decade-long, $6-trillion debacle in Iraq, you'd think Congress and pundits would be pressing the Obama administration for figures: If the U.S. fights ISIS in Iraq and Syria, what would be the odds of victory? How much would it cost? How many U.S. troops would be killed? How would it effect nearby countries like Iran? And how much of a threat does ISIS actually pose to the U.S. "homeland"? Yet much coverage of Syria is narrowly drawn. Vital questions are studiously ignored, as if they have no bearing on the merits of intervention, while dire warnings are presented with too much hype and too little rigor.