It's like saying in a FPS shooter you start to kill someone a lot so you get less bullets or less HP. How would that be fair?
The solutions described here give advantages to the losing side. The winning side is not handicapped.
On the other hand, to use your analogy, the game currently awards HP and bullets to players who kill their opponents. How would that be fair?
The answer, I think, is that it's a faulty metaphor. An FPS has very little disparity between any given player: a badass and a noob have the same tools at their disposal, and the only difference are the players. Counterstrike can potentially have some differences due to money collection, but I think that difference doesn't significantly affect the gameplay.
I totally disagree with this. It's a cheap mechanic that replaces skill with equality, which is unfair to skilled players.
I would agree with this if Demigod was designed first and foremost as a sport; something whose overall intent is competition. However, it's not; to me, the overall intent is making games as interesting as possible for a healthy amount of time.
The idea is that you give the losing side opportunities to turn the tide of the game. You don't give them anything absurd, and you could even make them triggered as rewards.
For example, the losing side has both portals capped. As a reward for recapping them both, they're both locked for X minute(s). This gives the losing side an opportunity to push back.
There's two important things to understand with the balancing idea. First, Demigod is a game, not a sport. The overall motivation of developers is to make the game as fun as possible for all players. Second, the perfect balancing system doesn't actually affect the outcome of the game. It should only make games closer and consequently more interesting. It should not flip outcomes.