Small gestures can convey profound feelings. After the Paris massacres, seeing flags flying half-mast in Washington moved me. That traditional gesture proclaimed America’s support for France, whether or not President Barack Obama deploys troops against Islamic State. Seeing French flags waving throughout Jerusalem was even more moving. That display showed Israel’s empathy for others’ suffering, despite our woes, despite the EU’s incendiary, infuriating labeling of settlement products.But why aren’t Israeli flags flying in Paris and elsewhere in solidarity with Israeli victims of terrorism? And why aren’t Israeli flags flying all over the United States, the home of murdered American citizens, including 18-year-old Ezra Schwartz, who was in Israel on a gap year program? We need a massive social media campaign, led by everyone who is, was, or will ever be on an Israel program – and their leaders – to wave Israeli flags in Ezra’s memory.The 21 Israelis killed since October deserve more than an Israeli flag waved or heartfelt words from strangers.Each deserved to live a full life. Each has been robbed of that basic right by terrorists and the terrorists’ supporting cast: Palestinian co-conspirators who often dispatch marginal people to commit these crimes; Palestinian demagogues who incite, riling up even pre-teens with hate speech, ugly songs, despicable cartoons; Muslim preachers who inflame, using Islam to spread evil not good; Blame Israel Firsters who don’t hold Palestinians to basic civilized standards, rationalizing Palestinian crimes while criminalizing Israeli acts of self-defense.And terrorism is terrorism, even if you consider the West Bank occupied. Despite blaming “lone wolves,” the Palestinian Authority has shifted most (not all) terrorism from Jerusalem to the West Bank. Since 9/11, the Palestinians have tried to avoid being tagged as terrorists, because it hurts their public opinion war. Palestinians understand how to play the game in a world in which US Secretary of State John Kerry can distinguish between the Charlie Hebdo massacre, which had “a sort of particularized focus and... a rationale you could attach yourself to somehow,” and the “absolutely indiscriminate” Paris massacre. To many, attacks in Israel, and certainly in the West Bank, have that Kerry “rationale” where you can say, “OK, they’re really angry because of this and that.” Hearing about a sweet, innocent, 18-year-old American shot through a car window, while sitting in a minivan stuck in traffic, should prove that Palestinian terrorism is “indiscriminate,” whatever you think about Israeli policies.Ezra Schwartz’s death was as tragic as the deaths of the others his murderer killed: Yaakov Don, 51, a beloved educator and father of four, and Shadi Arafa, a 24-year-old salesman for the Palestinian cellular operator Al-Wataniya.Yet, Ezra’s death is resonating more, particularly among Americans, and American Jews.Many of us feel we knew him by hearing the sketch of his too-short life. It’s all-American: happy family... summer camp... baseball... high school graduation... accepted to Rutgers. It’s familiarly Jewish: Camp Yavneh... Maimonides High School... an Israeli “gap year”... killed after distributing food to soldiers and doing other good works. It does not negate his uniqueness, the “loving, caring and fun-loving” person one friend eulogized, to imagine his parents’ love for him, his siblings’ delight in him, the joy, exuberance, generosity and great potential killed with him.At his son’s funeral, Ari Schwartz acknowledged the love flooding in from all over, saying: “We are proud to be part of the greater Jewish community that connects us throughout the world.” And elegantly ignoring Obama’s pinched, delayed condolences, he thanked the Israeli and American governments for their wishes, saying: “It made us feel that he was important. Every person is important.”Every person is important. But because Ezra Schwartz’s death has this extra American resonance, we have extra work to do. As his family contemplates a lifetime ahead of family celebrations with one perpetually empty chair, one loved one who will never show up physically but will never leave them spiritually, we should send them love by displaying an Israeli flag – or the Israeli and American flags together – in Ezra’s memory. Post a selfie of yourself and that flag on social media, encouraging your friends to follow your lead. Send that photo to firstname.lastname@example.org.Wave that flag for Ezra and all terrorism victims, in Israel and worldwide. Wave it to end this bout of Palestinian terrorism, and all terrorism. Wave it to stop the ugly incitement, the evil enabling, the revolting rationalizations. Wave it to encourage Obama to grow a spine and mobilize American law enforcement resources against these killers of Americans while sanctioning PA President Mahmoud Abbas until he blocks the incitement. And wave it to show that the Schwartz family is not alone, the other victims’ families are not alone, Israel is not alone.During Hanukka, 1993, in Billings, Montana, anti-Semites shattered a window in a Jewish home decorated with a paper hanukkia. The police, fearing more violence, advised the family not to replace the menorah in the window. Christian neighbors mobilized, inspired by the Danes who wore yellow stars to support their Jewish fellow citizens under Nazi rule. As many as 10,000 people displayed menorahs in their windows. When asked whether this gesture might trigger more vandalism, the police chief replied: “There’s greater risk in not doing it.”Imagine if, on Thanksgiving, the Schwartz family awakens to find their town of Sharon festooned in blue and white, and sees photos of Israeli flags throughout Massachusetts, America, the world. It won’t bring poor Ezra back. It won’t minimize the loss. But it will help give this tragedy some meaning, showing Palestinian leaders that Americans and the civilized world recognize this violence as terrorism – and are disgusted – even when terrorists target Jews, even on the West Bank.Remember: There’s greater risk in not doing it.The writer is the author of The Age of Clinton: America in the 1990s, just published by Thomas Dunne Books of St. Martin’s Press. He is professor of history at McGill University and a Visiting Scholar this fall at the Brookings Institution. Follow on Twitter @GilTroy www.giltroy.com.