Cartoon physics. Similar rules. That's all. Reading more into the show is as useless as applying logic to Bugs Bunny. It reminds me of the Road Runner Laws & Rules. The most applicable rule is #3, "The Coyote could stop anytime — if he were not a fanatic. (Repeat: 'A fanatic is one who redoubles his effort when he's has forgotten his aim.' — George Santayana)."

Marv and Harry could've quit at anytime.

If they live in a cartoon universe, then Kevin's actions are as sane as the Road Runner and Bugs Bunny. He's not crazy, Marv and Harry are.

Cartoon universe also explains the utter lack of concern by nearly everyone else involved — the police, the airline, most of the family.

After so many efforts to avoid the fight with Marv and Harry, I can almost hear Kevin say, "Of course you realize, this means war!"

BTW, Marv and Harry are the real stars of the show and dominate the last third of the runtime. My family absolutely loves the last act of Home Alone 2.

"That was the sound of a tool chest, falling down the stairs."