"What Syria does/or doesn't do is nobody else's business"
Are you seriously suggesting that when an oppressive regime embarks on a killing spree, with its own citizens on the receiving end everyone else should just look the other way, saying 'it's none of our business'?
There's a good deal of international concern over what is happening in Syria, but options are - at the moment - limited. The consensus of opinion is probably that the Syrian regime doesn't have much longer before it collapses, and that it's better, in the long run, to allow the inevitable to happen, rather than risk the many problems associated with a military intervention of any kind.
That depends on who you believe - the Turkish authorities, who say their aircraft was on a routine training mission, and was 13 nautical miles off the Syrian coast when it was engaged and shot down, or the Syrian authorities, who say it had 'penetrated' their airspace.
Turkey admits that the aircraft 'momentarily' entered Syrian airspace by accident, and immediately made a turn when this was realised.
Now, imagine you are a Turkish air force commander - would you allow a 'routine' training mission to fly so close to the airspace border of a country with whom relations are - to put it mildly - somewhat tense? The Syrians are saying they didn't realise, at the time, that this plane was Turkish, but that takes a bit of swallowing. One wonders just where they thought it had come from. A normal response to seeing an unauthorised military aircraft in your airspace would be to put up an interception flight, and warn the pilot that his aircraft would be fired on unless he made an immediate exit. That they didn't do this is an indication of just how jumpy they are.
Turkey will consult with other NATO allies before responding - let's hope the advice is to make a huge fuss and nothing more. The very last thing the world needs is retaliatory action that could precipitate an all-out state of conflict in the region.
"Let the Iranians and the Turks etc. get on with it."
Unfortunately there's that little stumbling block called NATO, and we can't simply ignore what happens when a NATO ally is involved. Turkey is a NATO member, so we are committed to safeguard the freedom and security of the country by political and military means.