Well, no kidding. After 9/11, after the Madrid and London transit massacres, it is hard to imagine anyone objecting to Romney's statement of the obvious. But object they did. The ACLU accused the governor of proposing ''another giant stride toward a police state." The Council on American Islamic Relations, shamelessly distorting Romney's words, said it was aghast that any governor would ''suggest blanket wiretapping of houses of worship." Groups from the leftist fringe staged a protest outside Romney's office.

But if they expected to browbeat him into an apology, they were disappointed.

''This thing is just common sense," he told reporters. ''Surely we have to recognize that some of this has gone on in mosques in the past . . . . There have been places of extremism where certain teachers have been identified as having been involved in . . . terrorist attacks. Let's not pretend that's not the case."

Again, a statement of the obvious. But imagine the reaction if Romney had said something not so obvious. Say, like this: ''The most dangerous thing that is going on now in these mosques . . . is the extremists' ideology. Because they are very active, they took over the mosques; and we can say that they took over more than 80 percent of the mosques that have been established in the US. And there are more than 3,000 mosques in the US."

An American politician who uttered such thoughts would be smeared as a bigot. But it wasn't a politician who said them. It was a Muslim scholar and humanitarian, the Sufi sheik Muhammad Hisham Kabbani, speaking at a State Department forum in 1999. Kabbani was one of the first moderate Muslim leaders in the United States with the courage to publicly denounce the extremists. Unfortunately, his alarm didn't wake Americans from their pre-9/11 slumber. But what excuse can there be now for not taking seriously his warning that most US mosques are in the hands of a radical minority? As Romney says, ''This thing is just common sense."

There would have been no hullabaloo if Romney had spoken of ''monitoring" and ''wiretapping" what was being discussed by suspected gangsters meeting in the back rooms of Italian restaurants. Or of ''seeing who's coming in, who's coming out" of a housing project where drug deals take place. It was the focus on mosques that caused hackles to rise. Freedom of religion is an engrained American value, and the prospect of singling out Muslim houses of worship for special scrutiny leaves a bad taste.

But if Americans want to protect themselves from Islamist terrorism, monitoring the mosques that foment it must be a priority. Needless to say, this must be done legally. Romney isn't proposing to do away with safeguards like judicial oversight and warrants issued only for probable cause. ''I don't want to change the rules," he emphasized in an interview last week. ''You can wiretap only when you comply with the Constitution."

The evidence that some radical mosques have been perverted into terrorist hatcheries has been mounting for years. The notorious Finsbury Park mosque in London incubated jihadists for holy wars worldwide; among its alumni are Zacarias Moussaoui, the alleged 20th hijacker, and shoe bomber Richard Reid. Brooklyn's Al-Farooq Mosque is where Sheik Omar Abdul Rahman, a rabid Egyptian cleric, incited his followers to bomb the World Trade Center in 1993.

Just last week, Hamid Hayat of Lodi, Calif., was indicted on federal terrorism charges; he is one of five suspected jihadis arrested earlier this year. All five attended the same Lodi mosque, and allegedly took direction from its two imams, Shabbir Ahmed and Adil Khan -- both of whom have now been deported to Pakistan.

Romney's position is the only responsible one. We will never be safe from terrorism so long as enemies within our borders keep spreading the plague of Islamist violence. Homeland security depends in part on monitoring those enemies and knowing what they're saying. Even when they're saying it in a mosque.

Jeff Jacoby's e-mail address is jacoby@globe.com.