"Bombings and chemical attacks like the ones that almost led Britain to war in 2013,"
Assad is fighting ISIS as little as possible, and the groups actually fighting him are not separate from the anti-government sentiment,
"President Assad’s forces are fighting a civil war on several fronts – against Isis, other Islamist militias, secular rebel groups and to quash the anti-government sentiment that started in the 2011 Arab Spring,"
Assad's attacks aren't against the majority of foreign fighters fighting on his side of the conflict,
"At least 100 fighters, the presumed target of the regime's attacks, were killed in the same strikes, including rebels, Islamists and foreign militants on both sides of the conflict,"
Nobody but Assad is using barrel bombs,
"The Syrian Observatory for Human Rights is calling on the Security Council to issue another resolution condemning al-Assad’s regime for its “indiscriminate bombing” and to order all parties in Syria to stop using barrels bombs,"
ISIS and Jabhat al-Nusra are not the same thing, the latter fights Assad,
“The extremist group Islamic State and al-Qaeda’s affiliate in Syria, Jabhat al-Nusra, were responsible for systematic and widespread violations including targeting civilians, kidnappings, and executions.” "