The carrying capacity of the earth is not static. Technological advancements continually expand it. We aren't living in a glass bottle, but a rubber balloon.
True. Without nuclear energy we have already passed the carrying capacity of the earth. If we keep using polluting fresh water (with mercury) and keep polluting the air at this rate we will start to die off from disease at a faster rate. With nuclear we can have a much higher population without damaging the earth to the point where it damages us back.