Whilst I understand that, you could argue that that is exactly why both sides need to sit down and talk.
This cannot go on for ever, at some point both sides have to accept violence will never be the answer. What's happened (terrible as it is) has happened and we can never go back in time to change it.
The only way violence will work is the total eradication of one side or the other. That can never be the right path to go down.
We can all sit here online and say we'll never talk to terrorists, Margaret Thatcher made a great public speech with that line yet it turns out our government had channels open all the time.
I have no answer as whoever tries to step in usually has their own interests at heart.
UN maybe? Then again others will vote against whoever their current 'enemy' is purely because they can. For instance Russia will never back anything put forward by the US, and vice versa.