You mean "moderate terrorists"? What is the difference between ISIS and "rebels"?
Well quite a few of the rebel groups consider ISIS an enemy, for a start. However Assad would consider them all terrorists as they are all against him.
There is definitely a different point of view of who is a terrorist depending on who you ask, the Turks would definitely disagree on the Turkmen being terrorists but would probably call the Kurds terrorists while the US and Russia would not. It's one big mix and the label "terrorist" is really more about who is on whose side than on what they are actually doing.
Anyway, Syria is a big country with lots of baddies to bomb. Without detracting from the fact that Turkey was completely in the wrong to shoot down this plane, why does Russia feel the need to do things which it knows Turkey is very very annoyed about already? The Turks protested incursions weeks ago, and just this Friday complained about the targeting of people it considers on "their" side. Did Russia take any of that into account, or did they simply carry on as always and fly right on top (and probably just across) of a country that has shown itself to be too trigger happy already. Why the need to ignore Turkey's anger and put trust in them not to overreact? How hard is it to stay a couple miles further away?