In a speech before his supporters on Monday, Mr Donald Trump, the leading United States Republican presidential candidate, shocked the world when he proposed that the US should ban all Muslims from entering the country until American leaders "can figure out what is going on".

Despite widespread condemnation, Mr Trump has stood by his idea, saying it would be a "temporary measure" in response to the threat of terrorism from militant groups. He invoked one of America's darkest periods: President Franklin D. Roosevelt's decision to detain thousands of Japanese, German and Italian immigrants during World War II.

Mr Trump's proposal is reprehensible, and it is part of a growing trend of Islamophobia that is making life difficult for the three million Muslims in the US. I am one of those Muslim immigrants who have made our homes in America and assimilated into a vibrant and often welcoming society.

Already, hate crimes against Muslim Americans have increased since the Nov 13 terrorist attacks in Paris and the Dec 2 massacre in San Bernardino, California - with one civil rights group logging at least two dozen anti-Muslim attacks over a three-week period.

And Mr Trump is not the only presidential candidate who has fanned the flames of anti-Muslim hysteria.

After the Paris attacks, Dr Ben Carson, a retired neurosurgeon who is also a candidate for the Republican nomination, described Syrian refugees as "rabid dogs". He has also falsely claimed that Islamic law requires that "people following other religions must be killed".

The stereotypes perpetuated by Mr Trump and other demagogues have more subtle effects than outright violence. They shape a social climate in which all Muslims and Arabs are treated as potential terrorists. One national poll released last month found that more than half of Americans believe that Muslims should be barred from seeking the presidency, while 56 per cent of US citizens see Islam as "at odds with American values".

Of course, it is Mr Trump's proposed ban on Muslim immigration which is at odds with the historic American ideals of religious freedom and tolerance. Beyond the damage he is causing to America's image and values, he is also handing a propaganda victory to the militant forces that he is supposedly trying to defeat, especially the Islamic State in Iraq and Syria (ISIS).

Mr Trump's latest antics play perfectly into ISIS' hands, confirming the group's message that the West is an evil, hostile land where Muslims are unsafe and where they will be persecuted simply for being Muslim. One of the pillars of ISIS' ideology is that it is the true - and only - defender of Sunni Muslims, who are being persecuted in Syria, Iraq, Lebanon, Egypt and everywhere else where ISIS has carried out attacks, either directly or through its affiliates.

In its slick propaganda, ISIS emphasises two major themes: a righteous and idyllic life for "true" Muslims in its self-declared Islamic state in parts of Syria and Iraq, and an ideology that sanctifies violence as the only means for Sunnis to achieve power. The group is highly sophisticated in its use of social media to sow fear among its enemies, and to entice alienated Muslims living in the West to "immigrate" to ISIS-controlled territory.

Never mind that ISIS selectively uses a group of clerics and scholars from across Islam's history who advocated declaring other Muslims as infidels or apostates, and justified their killing. The majority of the world's 1.6 billion Muslims reject this notion of takfir. But it is central to the ideology of most of today's militant groups, who have killed far more Muslims than non-Muslims.

That fact becomes obscured as long as ISIS has new opportunities to portray itself as the defender of Muslims.

One reason ISIS and other terrorist groups have had greater success in recruiting Muslims living in Europe, as opposed to the United States, is that Muslim communities are more alienated in Europe. In America, Muslim immigrants tend to be more educated, diverse and affluent than their counterparts in Europe.

In a report released on Monday, the Soufan Group, a New York-based security consultancy, estimated that between 27,000 and 31,000 foreign fighters have travelled to Syria and Iraq to join ISIS and other extremist groups. About 5,000 of those fighters came from Western Europe, mainly from Britain, France, Germany and Belgium. By contrast, only about 250 Americans have tried to join such groups in Syria and Iraq.

But thanks to Mr Trump and other demagogues who are using the San Bernardino attack to whip up anti-Muslim fervour, a new backlash against Muslims in America will breed a greater sense of resentment. And ISIS knows well how to exploit that alienation.

• The writer is a journalism professor at New York University and a former Middle East bureau chief at Newsday, a New York daily paper.