1) 60000 killed in 22 months is a an exxageratio/ lie. This means 2800 per month. The opposition leader is a dumb clergy man and knows nothing about government and politics. In addition his views, program and agenda are unknown. First of all he has to present his program before going into negotiations.
ISIS kills 22 in Yemen's Sanaa, Aden; targets both gov't and Houthi rebels (Reuters)
from the article: Syria top opposition leader says willing to negotiate with Assad