"— let us surrender so we don't get massacred."

There are many times in a GM's life when the players will do something ridiculously stupid and reckless, which would lead to them getting killed if it happened in reality. At times like this, you throw them a lifeline. You offer them the chance to surrender gracefully and accept an alternative, non-lethal setback, that could lead to interesting situations and adventure in itself. At which point the players will blithely ignore it and charge ahead anyway.

And then you can let them have it.

Transcript

GM: You see a squad of a dozen battle droids, each armed with a blaster. You're completely outnumbered and outgunned. There's no chance of escape.
OWO-1: Lay down your weapons and—
Qui-Gon: Attack!
Obi-Wan: What?!
Qui-Gon: We attack!
Obi-Wan: No, wait, the GM's trying to—
Qui-Gon: I roll a 20!
[SFX]: Whooom!
[SFX]: Krzzzsh! {Qui-Gon chops a battle droid's head off}
Obi-Wan: They have blasters! All we have are these dinky laser swords!
GM: It's their turn. They aim their blasters.
Obi-Wan: We have no defences!
GM: You should have thought of that before you went off my plot rails.