If jumping out of a window usually leads to uncontrolled descent and flight into terrain, which then leads to experiencing a very large and sudden velocity change, which is followed by death from the injuries caused by said ∆v/∆t, I'm definitely going to argue against jumping out of a window. Sure, for the above A->B->C->D(eath) chain, there are many ways to prevent it from reaching the last node, but the default behavior is still A->B->C->D, so it's fair to argue against doing A without evident mitigations of steps B and/or C.

But if you're arguing not to jump out a window, and I have base jumping experience and am wearing a parachute, the argument is silly. Especially if the building is on fire.

Slippery slope arguments assume A leads to D and discard any positive effects A could have out of hand. That's why they're a fallacy.