Did Gollum deserve death?

[Thenamir]

Originally Posted by davem

My feeling is that they don't kill him because they never actually needed to - killing in self defence is one thing. Executing someone in cold blood is another. I'm uncomfortable with the idea that they simply kept Gollum around because he might prove 'useful'.

I am in agreement here -- it was quoted earlier that even orcs were given mercy if they asked.

Originally Posted by The Field of Cormallen

And those that were deepest and longest in evil servitude, hating the West, and yet were men proud and bold, in their turn now gathered themselves for a last stand of desperate battle. But the most part fled eastward as they could; and some cast their weapons down and sued for mercy.

Though the text does not explicitly state what happened after this, the expectation is that those who asked mercy were given it, and the ones who continued fighting were probably slain or driven off.

Gandalf said "Do not be too eager to deal out death in judgement" [emphasis mine] This says nothing of dealing out death in clean battle, only (in my opinion) of pronouncing sentence on deeds done previously.

[Kuruharan]

it was quoted earlier that even orcs were given mercy if they asked.

-and-

And those that were deepest and longest in evil servitude, hating the West, and yet were men proud and bold, in their turn now gathered themselves for a last stand of desperate battle. But the most part fled eastward as they could; and some cast their weapons down and sued for mercy.

That passage does not refer to orcs.

Note:

And those that were deepest and longest in evil servitude, hating the West, and yet were men proud and bold

The orcs were...

orc or troll or beast spell-enslaved, ran hither and thither mindless; and some slew themselves, or cast themselves in pits, or fled wailing back to hide in holes and dark lightless places far from hope.

It didn't occur to them to beg for mercy. They weren't rational anymore.