Unless you live in Russia or Syria, it's not, and shouldn't be, your problem.
And if a large majority of Syrian citizens are against further arming Assad's regime? Whose problem does it become? If they ask or beg for the UN to impose a no-fly zone to counteract the Assad regime's airstrikes, whose problem does it become, these new(er) anti-aircraft missiles?
Just curious at how far regimes can descend, before action is taken. Is it a utilitarian argument, where the balance of lives saved must outweigh the lives lost in escalating the rebellion or outright toppling the regime? Is it an argument for means justifying the ends, that there's a tipping point where offensive military action or aid is justified (Saudi Arabia, Qatar and Turkey already think so)? Does it change the equation if not stopping the Syrian conflict will inevitably draw Lebanon, Israel and probably Iran, Turkey and the United States into a wider and messier conflict? Would it change the equation if Assad had 10,000 artillery pieces aimed at Istanbul?
The point of all these questions is foreign policy is difficult and nuanced. No two situations are alike, and although we'd like it to play out like a domestic law enforcement problem, it never does and it necessarily can't be. Leaders and nations following simple rules to a fault, such as "Unless you live in Russia or Syria, it's not, and shouldn't be, your problem" tend to make a fucked up mess of things, either through gross inaction or not-well thought out action, like George W. Bush.