clearstream
(He, Him)
I agree with you. It does seem improbable that the spell was designed to have that function![MENTION=71699]clearstream[/MENTION] I think your ruling was fair and supported by the rules you quoted. It seems unlikely that the intention is magic missile is a spell NPCs or monsters use to snuff out dying PCs, especially as it wouldn't work the other way unless the DM is using the dying rules on NPCs or monsters.
That's what I found quizzical: that the mechanics as written yield an "evil" spell.