Moreover, these demands are harmful to US security interests - redefining US anti-ISIS mission to one of anti-Assad mission - and thereby potentially drawing in Eurasian powers of China, Russia and Iran into open military conflict against the US.
Presently the Beijing-Moscow-Tehran axis is actually tacitly supporting the US-led coalition, and Assad is allowing US use of its airspace to strike ISIS and other Islamic extremist groups.
Comment: The Beijing-Moscow-Tehran axis are playing it very cool, very smart, and very sane right now. They do not want war but they can also see the writing on the wall given the patterns of the US-led coalition's actions.
Now, Ankara, Riyadh and Doha's obsession on removing Assad and hoping to replace him with a proxy Islamist regime is throwing a monkey wrench into coalition efforts. With Islamist strongholds spanning from Turkey, Syria, Lebanon, Gaza and Egypt, this risks turning the Eastern Mediterranean into an Islamic Lake, a threat shared by Israel as well as EU members Cyprus and Greece.
This is also a threat to US' Noble Energy, Italy's ENI, Korea's KOGAS, Russia's Gazprom, and other stakeholders such as Jordan, Egypt, and Asian consumers interested in the newly discovered natural gas resources in the Eastern Mediterranean.
As such, removing Assad for a probable Islamist replacement that will also persecute the Christian, Kurdish, Druze and Alawite communities in Syria; escalate the conflict by drawing in two nuclear powers of China and Russia; harm development of hydrocarbons in the Levantine Basin and further regional instability, is not in US or EU's security interest.
And it is definitely not in China's interest.
Comment: If it seems like the U.S. has entered into a maniacal and suicidal attempt to impose military and economic power over some of the largest and most independent nations on the planet, it is because they are.