There are millions of Muslims that are completely peaceful and well integrated in Western society (they speak the local language, obey the laws of the land etc.) however there is also a much smaller group of Muslims (whether terrorists or not) that completely refuse to integrate.
They refuse to learn the language of their new country, they only want to live and associate with other Muslims and they refuse to accept the laws of their new nation.
It's these people, that refuse to integrate with society, that are the problem. How on earth do you address this though? Deport anyone that doesn't speak English? I don't have any answers but we shouldn't tolerate people in a society that refuse to integrate and contribute to that society (whether they are Muslim or Christian or Buddhist or Atheist).