Perhaps that is because you have not been listening, or perhaps because this has been poorly reported. For example, in 2015, 70,000 Muslim clerics passed a fatwa against global terrorist organisations like the Taliban, al Qaeda and ISIS (http://www.huffingtonpost.com/entry/muslim-clerics-condemn-terrorism_us_566adfa1e4b009377b249dea). Recently, a list of over 5,720 Muslim groups and leaders denouncing terrorism was compiled (http://www.teenvogue.com/story/teen-makes-spreadsheet-muslim-groups-leaders-denouncing-terrorism). Any quick Google search will pull up lots of examples of Muslim clerics and intellectuals (and common folk) banding together to condemn terrorism.