Forget Israel's Gaza security fence — What are other fences for?

As a kid, a fence was just something you jumped over, unless it was too tall and then you climbed over. My brother taught me how to "jump fences" – get over fences between backyards really fast.
"Y'never know when it's gonna save y'life" my brother sagely said.
"Huh what?" I sagely asked.
"Ya, let's say you gotta getaway real fast from some big kid who's gonna beat ya inta a pulp. Run the sidewalk – he's gonna getcha' cause you're a runt and he's bigger," my brother explained.
"Naw; if he's bigger he's fatter and I'm gonna getaway easy," I declared confidently.
"Naw, you're a little kid so you ain't learned physics. Taller means longer legs, he's going farther than you for every step, so he's gaining on you," my brother gave me my first lesson in Newtonian physics.
I became convinced of the scientific necessity of learning how to escape a potential assailant by learning how to "jump fences." I never bothered to ask my brother what if the bad guy knew how to jump fences too, because I knew from movies that the good guys always knew these neat tricks that made the bad guys look dumb, and movies only tell the truth, right?
That's how I learned as a kid that fences in my neighborhood were especially put there to help me escape the bad guys. It may have saved my life at least once. It was snowing so I was walking in the ruts made by the cars in the side streets. Whenever a car came at me I'd step aside, but one car swerved toward me.
Feeling a strong urge to express my displeasure with the driver's behavior, I extended my right hand toward that car and lifted my middle finger to point at the sky. Immediately their brake lights went on and the car started backing up. Not wishing to meet them, I took off straight for the closest fences, skipping from backyard to backyard, breaking through a front yard to cross the street to the next row of backyards, until I felt safe. I learned from that experience how to curb my urges of creative expression.
After growing up I learned that fences were actually there to keep little runts like me out. They say fences make good neighbors. I guess that's true only if you don't try to jump those fences.
I never know who they in "they say" is, but they say they can be trusted if they say something. I don't know, because I see that they say a lot of nonsense and interpret the facts in different ways – distortion actually – in order to confirm preceding prejudice and ideology, rather than drawing conclusions from the facts.
I guess that's the difference between "them" and "they," the difference between actual facts and knowledge and opinionated ideology
The fences between Israel and those that wish to kill Jews, and other such amusements, are there not to be jumped over, cut or breached. They're meant to protect people, like fences all over the world.
When Hamas leads a "March of Return," they mean to do the Jews a lot more harm than I had to fear from that snowy day in Chicago years ago. Ten thousand people reaching the fence and cutting through – that's a hostile invasion and an overture to pillage, murder and kidnapping. It's an invasion, period, and every sane country will resist invasion, whatever it takes.
I've heard otherwise intelligent people ask: But sixty Arabs killed and no Israelis? That's disproportionate!
Proportionality doesn't mean that if ten gangsters are killed by the police then the gangsters get to kill ten policemen! It doesn't mean that if the attacker has a sword you can't use a gun to defend yourself (think Indiana Jones). It means not to use more force than necessary.
That's exactly what Israel did the other week: after dropping leaflets warning that coming close to the fence may be hazardous to your health, after using tear gas and other anti-riot measures, there were that still those that made for the fence: Hamas (50) and World Jihad (3) operatives. The only thing that stopped them was exact, limited live fire. That's exactly proportionality.
If you think Israel had no right to defend itself you're calling for its destruction. That's anti-Semitism, not justice.