Significant portions of "American" muslims favor sharia law over the Constitution. There would be no penalty for Female Genital Mutilation under that regime of law. Women and LGBTs are relegated to "second class" status at best, having far fewer rights than muslim men. I just listened to a 7 minute report this morning on NPR talking about the treatment of gay men in Chechnya (94% muslim), where they are often beaten if not killed. In the entire seven minutes the reporter only said the word "muslim" twice, and never uttered the word "islam".
Even if you think this poll and/or the organization that sponsored it are "islamophobes", there are other polls from Pew and other more "mainstream" polling organizations that confirm the results within a few points. Even if the poll is off, on the over-estimate side, by a factor of 10, that would still leave thousands of muslims in the U.S. who believe that "the use of violence in the United States is justified in order to make shariah the law of the land". (The poll cited "nearly one fifth" suported such violence. Of the 3.3 million American muslims, that would be 660,000. If the poll was off by a factor of 10 (almost impossible given other polls by other organizations) that would be 66,000 who believe violence is justified to establish sharia law in the U.S. That's a LOT of potential damage...).
* * * * *
According to the just-released survey of Muslims, a majority (51%) agreed that “Muslims in America should have the choice of being governed according to shariah.” When that question was put to the broader U.S. population, the overwhelming majority held that shariah should not displace the U.S. Constitution (86% to 2%).
More than half (51%) of U.S. Muslims polled also believe either that they should have the choice of American or shariah courts, or that they should have their own tribunals to apply shariah. Only 39% of those polled said that Muslims in the U.S. should be subject to American courts.
Even more troubling, is the fact that nearly a quarter of the Muslims polled believed that, “It is legitimate to use violence to punish those who give offense to Islam by, for example, portraying the prophet Mohammed.”
Nearly one-fifth of Muslim respondents said that the use of violence in the United States is justified in order to make shariah the law of the land in this country.
https://www.centerforsecuritypolicy.org/2015/06/23/nationwide-poll-of-us-muslims-shows-thousands-support-shariah-jihad/About 14% of Muslims in the nations surveyed (and 8% of Muslims in the US [264,000]) said violence against civilians is "often" or "sometimes" justified.