There bad apples in every barrel and unfortunately these bad apples all too often gain a great deal of power and influence. It is highly unfortunate.
Maybe the moderate muslims are silent because they feel like whenever they speak up, one or another, they'll just get bullied and brow beaten for it. Or maybe they are speaking up, and you just aren't listening, or are unable to hear them because the stories of these muslims are not as "eye-catching" and thus are not given the attention they deserve, causing them to be drowned out by the bad apples who can bring more eye-catching headlines.