Throughout his presidency, President Obama has emphasized one point while talking about Islamist extremists: They are not practicing Islam, he has said, they are perverting it.

He took that a step further Wednesday night. While announcing that he's expanding the campaign against the Islamic State extremist group into Syria, Obama said flatly that this group, which is trying to install a caliphate in the Middle East, "is not Islamic." He didn't say they are perverting their religion; he said they're not even part of that religion.

"No religion condones the killing of innocents, and the vast majority of [the Islamic State's] victims have been Muslim," Obama said. (Obama refers to the group as ISIL; more on that here.)

President Obama said the U.S. will work with a "broad coalition" of foreign partners to combat the Islamic State in his public address on Wednesday, Sept. 10, 2014. (The Associated Press)

While the rest of his speech avoided polarizing language, this statement stands out. That's because it's very polarizing. And, in fact, Americans are more inclined to disagree with Obama on this point.

A Pew Research Center poll released just hours before Obama's speech showed that 50 percent of Americans see Islam as a religion that "is more likely than others to encourage violence among its believers." The figure's up sharply from earlier this year and is the highest since Pew started asking that question in 2002.

By contrast, 39 percent of Americans say Islam doesn't encourage violence any more than other religions — down from 50 percent in February. Here's how that looks, over time:

Not surprisingly, conservatives and Republicans are more apt to see Islam as a more violent religion. Two-thirds of Republicans believe this, while independents and Democrats are below 50 percent.

There's also a massive age gap, with 33 percent of young people and 64 percent of seniors (65+) saying that Islam encourages violence more than other religions.

This is understandably a sensitive topic, and it seems to crop up every time a Muslim perpetrates a violent crime (the 2013 Boston Marathon bombing, for example) or unrest erupts in the Middle East.

But here in the United states, data from Gallup in 2010 showed Muslim Americans were actually less likely than other religious groups to believe that targeting and killing civilians is sometimes justifiable. While 11 percent of Muslim Americans said this, more than one-quarter of Protestants and Catholics agreed with that statement.

Obama's statement that the Islamic State "is not Islamic" will surely be a topic of conversation in the hours and days ahead. Shortly after the speech, he got a little backup from none other than Sen. Rand Paul (R-Ky.), who said the Islamic State "is not a true form of Islam."

One can certainly argue that this group is perverting or isn't practicing a "true form" of Islam. But suggesting that its violence and its aim to install a caliphate have absolutely nothing to do with the Islamic faith is a much harder sell for most Americans.