I recently GMed my first real role-playing game in *Lady Blackbird* with a few friends who are also new to tabletop RPGs, and it went quite well except for a few parts. Here's an example; the basic scenario was (a few parts left out for brevity):

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> Me: "Okay, so you shoot the lock of the door. It's made of strong metal, and it doesn't break. An alarm sounds, and guards chase after you!"
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> 
> Player: "We all take off our jackets and stand on them."
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> Me: "Uhhh, okay...? The guards look at you strangely."
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> 
> Player: "I cast my lightning bolt at the ship. The ship is made of metal, and all the guards are electrocuted and die."
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> 
> Me: "Okay, yes, you cast your lightning bolt. The bolt shoots down from the sky, hits the roof of the ship, and collapses onto your party, incapacitating them."
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> 
> Player: "Wait, no! That doesn't make sense! The ship is metallic, so it should absorb the electricity and conduct it to the guards to kill them!"
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> 
> Me: "No, the force of the lightning causes the roof to collapse, and the lightning wouldn't get to the ground without hitting the roof anyway."
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> Player: "But this is a flying ship, it's all made of metal! It should just all conduct to the ground and electrocute everybody."
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> 
> *<snip: 10 minutes of irrelevant discussion>*
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> 
> Player: "Fine, so it makes the roof collapse. Doesn't the metal door collapse, too?"
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> Me: "No, the door is *under* the roof."
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> 
> Player: "The door collapses too, because the roof is also metal! If the roof collapsed, then the door should, also!"
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> Me: "The lightning bolt only hit the roof; it then collapsed and didn't go thorough."
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> Player: "They're both metal! They both collapse because they're made of the same thing!"
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> 
> 

And so on, ad nauseam. This eventually escalated into something like "Someone else should be the dungeon master, who doesn't want to kill us!" "You can't do anything with magic just because... it's *magic*." etc.

**What should I have done in this situation?** I feel like there could have been a better option than continuing to argue with the player and eventually reaching a semi-compromise (in which neither of us were particularly happy with the outcome).

I tried to follow the rule "let the player do what they want, but have consequences," ("Okay, yes, you cast your lightning bolt ... roof of the ship, and collapses onto your party"), but as you can tell, that didn't work out too well. The problem player simply launched an argument for why specifically and realistically his plan would work perfectly. I'm at a loss for **what to do to get the player to stop arguing and just go with it**, while trying to avoid going out of character ("No, this is what happens, and that's final. If you argue you lose 5 experience points" or something sounds like a *terrible* idea).