The trouble with this argument is that one can argue that anything which deprives players of the ability to keep fighting on their preferred side is unfun, and thus should be eliminated. Paralysis. Petrification. Unconsciousness. Death.
It would take a massive rethinking of combat paradigms to enable PCs to continue to participate meaningfully on their player's preferred side no matter what happened and yet still make the combat an interesting minigame with meaningful consequences.
To some extent, yes, but which hurts more? "My character died fighting for what he believes in" or "My character became a mindless thrall and murdered everything he cared for"?
Proclaiming something "objectively" true or false does not excuse you from proving it so.