Here is my opinion. People should mind there own business, meaning there is no moral justification to supply arms to any group, rebel or militia to fight oppression because this solution often doesn't work or it never worked... I stand to be corrected though. Just look at isil now, where did they get most of the arms they are using to cause terror? They are mostly caches of arms left in that region during the u.s and it's allied invasion of Iraq. They armed the rebel and we all can see the result of that till today years after the so-called dictator is dead. Libya is also a good example, it used to be a great country under the regime of the then dictator Gaddaffi but we also can see what has become of Libya today. Has funding and arming the rebel in the country helped the so called oppressed? The answer is no. It made the whole situation a mess and the people are the ones suffering now. Afghanistan is also the sane and Syria is on the brink of destruction. I am not in support of dictatorship but arming and funding the rebels isn't the best solution.
Diplomacy works and may alleviate douse some of the fire though it doesn't solve all the problem due to agreement/disagreement but it's better than outright war and destruction because history tells us this never works. My two cent.