Look, you are only look at this from one side, the Russian side, which I think is a bit odd. How is it the right of the United States to negotiate a deal about the ability for a sovereign nation to make it's own decisions? I'm still trying to comprehend how you can even come up with that.
Russia has steadfastly fought against forcing Assad to leave. At one point they said that it would be possible, but only after the country was made stable and then fair elections were done where Assad could still run for President. Well, when do you foresee Syria being stable in the near future when Russia is attacking not only ISIS by the Syrian rebels?
Lastly, Russia made threats against Norway recently with nuclear war over the fact they allowed 330 U.S. Marines to come there and train. Do you think you are dealing with a rational nation when they do something like that?
Russia's interest in Syria is keeping its bases on the Mediterranean and so far the only way it can do that is to support Assad, but this conflict is expensive for the suffering Russian economy and Russia is starting to take casualties, so if Russia had a chance to secure its interests with paying so much in blood and treasure, it is reasonable to think it would take it, but Obama has offered nothing but political slogans calculated to play well in the US but without relevance to ending the conflict in Syria.
Russia has every reason to distrust the US and especially the Obama administration and that means they have to wonder why Obama sent Marines to train in Norway. The same conditions could have been found in Alaska so why Norway? Was this intended as a provocation or was it just another example of Obama cluelessness?