Although one could argue Assad stepping down from power could be considered a recognition of his poor leadership and misdeeds, it is not a punishment inflicted upon him. Furthermore, being out of the position of power certainly does not excuse the atrocities Assad committed while he WAS in that role.
Bashar Al Assad is responsible for serious war crimes that have threatened security throughout the entire world. It would send the wrong message if he was not held accountable to the fullest extent possible under International Law. I understand that international laws can be limiting in scope, but any means possible to hold Assad accountable should be taken.
Bashar Assad is one of the worst war criminals in recent history, but has said that to bring an end to civil war in his country, he would consider stepping down from his office as Syria's president. Even if he does so, he must stand trial for his crimes against his own people. Those crimes are the very reason that he should step down, but stepping down is no punishment in itself, especially for Assad, who never had any desire to be involved in politics in the first place. The people of Syria should have their justice against Assad, even if he steps down. Besides, thhe results could be much worse for him if he doesn't step down and he is deposed by force.
If ever a world leader should be held accountable for war crimes, it is Bashar Assad. His repeated and systematic string of atrocities against his own people cannot go without severe punishment. If he were allowed to walk free, any future threats of punishment would be met with a clear aire of scepticism.
The rebels are the ones who are responsible for hiding in dense populated towns that the rebels announced they captured assad bombs rebels civilian casualties happen. That is like saying Iserial should be held accountable for war crimes for slaughtering civilians a few years ago.... It's called casualty of war, and he won't step down due to his alliance with Russia who is supplying them with weapons and soldiers.