The FBI had the Orlando gunman under watch — twice — and, after much consideration, decided to stop following him. Was this a mistake? Obviously, tragically so.

But in this massive lost opportunity to prevent a slaughter dwells a positive sign for our ability to stop future attacks. Law enforcement at least had its eye on him. Scarier would have been that it had never heard of Omar Mateen.

Protests against government surveillance programs tend to grow in the quiet stretches between terrorist outrages. Absence of immediate fear is when the critics can best downplay the stakes — that even one miscreant can kill large numbers, and with weapons far deadlier than assault rifles.

It’s when privacy advocates have the most success portraying surveillance programs as highly personal invasions of ordinary folks’ privacy. Actually, there’s nothing very personal in the National Security Agency’s collection of our communications metadata. Basically, computers rummage through zillions of emails and such in search of patterns to flag. The humans following leads have zero interest in your complaints about Obamacare, as some foes of the surveillance programs have ludicrously claimed.

In the Orlando case, co-workers had alerted the authorities to Mateen’s radical rantings. The FBI put him on a terrorist watchlist, monitoring him for months. He was taken off when investigators concluded he was just mouthing off. The FBI had reason to probe him again, but again he was turned loose.

That was a failure, but a failure highlighting a weakness in the surveillance laws. The FBI dropped the case because the standard for showing probable cause — evidence of a crime or intent to commit one — is too high for needle-in-haystack terrorism investigations.

(Note that a local sheriff was able to use Mateen’s ravings as reason to have him removed from security guard duty at the St. Lucie County Courthouse in Fort Pierce, Florida.)

The bureau clearly erred in expecting a real terrorist to be informed. That Mateen had expressed sympathy for both al-Qaida and the Islamic State — groups in conflict with each other — was apparently seen as a sign that the man wasn’t seriously engaged in their politics.

Perhaps not, but he seriously approved of their bloody activities. That should have spelled danger, especially when added to his history of mental instability and spousal abuse and possible sexual confusion (an apparently new consideration).

But the FBI has been dealing with thousands of cases of potential homegrown terrorists not unlike Mateen. It must also consider that expressing support for a terrorist organization is protected by the First Amendment right to free speech.

We need a new standard for potential terrorists inspired by online jihadist propaganda. Meanwhile, the public should back law enforcement’s stance on encryption. Recall the FBI’s battle to force Apple to unlock the iPhone of Syed Rizwan Farook, the San Bernardino gunman.

Privacy advocates have harshly rapped President Obama for defending the government surveillance programs he himself once criticized. There’s a simple difference between them and him (and then and now): Obama receives the daily threat reports, and they don’t.

Government surveillance programs do need rules. Court review is important. But it simply isn’t true that public safety can be maintained in the age of lone-wolf terrorism without considerable surveillance. And the risks advocates ask us to take on in the name of privacy should be addressed honestly.

The parade of major terrorist attacks — Paris, San Bernardino, Brussels and now Orlando — has sped up. The more horror the less the public cares about reining in surveillance activities. Defenders of privacy should recognize this reality and more carefully choose their battles. The quiet times seem no more.

Froma Harrop is a syndicated columnist. Follow her on Twitter @FromaHarrop. She can be reached by email at: fharrop@gmail.com.