The "relatively small" group of troublemakers you are talking about are symptoms of Islam that occur after Islam gains power.
The spread of Islam to western democracies is a new trend. How it is spreading is well-documented from observing other countries. When Islam gains political power, it quickly becomes more aggressive.
When the first Muslims arrive in a Western democracy, they keep a low profile and make few if any demands on their host nation.
Many quietly work as students, business owners, professors, doctors and other professionals, making good first impressions and gaining vocational respect.
When a large enough number of Muslims gather, they start requesting recognition of the
Sharia law . (Please see my previous post.) To forstall resistance and suspicions, they publicly condemn "radical" Islam and even seek well-publicized inter-faith dialogue and gatherings.
When Muslims gain critical mass in a few cities, they begin to penetrate their host nation. Muslim political candidates conduct public relations campaigns and file lawsuits against
alleged islamophobia, pressure public schools with Muslim students to hold
prayers towards Mecca, endow Islamic studies departments at universities, place imams as 'chaplains' in armed forces and prison units. Even now, there is a push for the Koran to be taught in public schools as a "tolerance agenda".
When the Muslim population becomes the majority and/or Islam gains control of a nation (e.g., Taliban in Afghanistan), Sharia law is imposed on the host nation, which is then
locked down against non-Islamic influences, including Christianity. The ideal Islamic state to their mind, is
Saudi Arabia, where
Sharia law is the only law of the land and
enforced without mercy.
Again, how this spread of Islam happens is well-documented, and worth noting as a threat to America, where we are already seeing Sharia law being fully implemented.
