Ok, cast your mind back [if you are old enough] to the Falklands conflict. The Argentinian air-force inflicted significant damage [sunk British ships and killed British forces] using French supplied Exocet missiles - were the French blamed for this? I recall the Thatcher government putting massive pressure on the French to cease further supply of these missiles, but the trigger was definitely in the hands of the Argentinians.
There's a world of difference between a government selling another recognised government arms and selling / giving them to an unrecognised, untrained and virtually leaderless set of rebels. It would be utterly irresponsible for me to sell bayonets to the gang down my street but perfectly acceptable for me to sell them to the British Army.