US Offensive on Syria

The US Air Force will strike back at Syria’s air defense if they interfere with US plans for bombing positions held by Islamic State militants (IS, formerly ISIS), according to recent reports. IS has a significant presence in Syria.
AP’s anonymous sources in the Obama administration revealed on Monday that the US is ready to ‘retaliate’ against Syrian President Bashar Assad’s air defenses if they attack American fighter jets launching airstrikes on Syrian soil. The US “has a good sense of where the Syrian air defenses, along with their command and control centers, are located,” AP informed.
Source RT

Let see if I have this right .. For reasons that are rather unclear to me the US has been supporting Syrians (and foreign fighters) rebelling against the Syrian government; this resulted in a brutal and ongoing war in which both sides but notably the anti-government side have been alleged to have committed numerous atrocities. The Syrian government has been shown to have the support of a large majority of Syrians and to be more friendly to religious minorities than their largely sectarian opposition forces, but the Syrian government has been deemed ‘illegitimate’ by the US

Arms from the US and its allies have fallen into the hands of ISIS, a brutal organisation that has taken over half of Syria and Iraq. The US plans to bomb ISIS in Syria but refuses to coordinate attacks with the Syrian government, instead they say they will work with the Syrian rebel groups, some of which are allied to ISIS.

These rebel groups will effectively tell the US air force where to strike. Should the USAF ‘inadvertently’ strike Syrian government positions and should the Syrian government defend themselves by shooting down US planes then the US pledges to destroy the Syrian air force and air defences.

And the Syrian people who have been suffering in the conflict(s) between their government, the rebels and ISIS will now, also, be bombed by the US.

This seems neither logical (in terms of achieving its stated end) nor humane (in terms of minimising suffering) nor legal (in terms of being endorsed by the UN). How is there not outrage at the obscenity of these proposals?