Those who are supportive or sypathetic of extremists are estimated to be 15-20% of the Muslim population.
lol.
What's so funny? We're not talking those who actually engage in terrorist attacks. Simply those who are supportive or sympathize with them. Considering that, 15-20% may very well be a conservative estimate.
Do you have any evidence? Then we can analyze it. Not saying you're wrong, but lets start with some evidence to support your claims.
