You're welcome to leave the city via some means that doesn't pollute the atmosphere. Walk, bike, etc. It's really whiney of you to feel so incensed that you can't just do whatever TF you want because "mah freedoms" when those activities are contributing to a degradation of the livability of the planet.
Yes, we as a species have reached the point where there are things we _can_ do that we _ought not_ do. Sucks I guess?
The Matrix AI robots do not really need humans to survive. They had a form of fusion. In reality the reason why they created the symbiotic relationship was as a kindness to their human supporters so that the human race would not go extinct.
They were the villains. It's established in the animatrix set of short films, that the machines did not perceive themselves as villains, and this is a common characteristic that cuts across most tropes of villainy. During a monologue, a villain will often equivocate their motivation with that of the hero. (you and me? we're really the same...)
Focus groups and producers interfered with that aspect of the plot (the grid computer made of people, hence the name: The Matrix), and rewrote the story to depict the machines as using humans as an energy source, a power grid (changing puns and quips using, instead of computational terms, to energy references, such as "coppertop" and the like), which tested as a more accessible concept to the lowest common denominator in the target audience.
If you watch the supplemental material included with the trilogy boxed set, I think it's mentioned in either one of the commentaries or the documentaries and interview segments.