It’s called Washington Monument Syndrome.

That’s shorthand for the way federal agencies react to any threat of budget cuts or a government shutdown: by closing down the most popular public services.

No one has mastered this better than President Obama.

Which explains the dramatic — and wholly unnecessary — confrontation Tuesday at the World War II Memorial on the National Mall. Faced with signs saying the memorial was closed, war vets rightly pushed past makeshift gates and barricades to make their visit.

That there were barricades at all underscores the phony politics at work.

The memorial is open-air, open 24/7, with no need for guides and staffers. In fact, the National Parks Service had to bring in seven workers — all exempted from their furloughs — to set up the ring of barriers.

In addition, the memorial by law was built and is maintained by private funds held in trust, so defunding the government should have no impact.

Not to mention that Democrats defeated a GOP bill that would have explicitly funded the national parks.

Why the pettiness?

Because Beltway Democrats are enjoying the shutdown and want to make it as painful as possible so they can paint their GOP opponents as crazies.

But here’s a question: If House Republicans are passing bills to fund the memorials and Democrats are voting against them to deny these funds, who are the real extremists?