If I remember well, it is sometimes possible for AIs to make subsequent demands from you in the same diplomatic conversation as their first demand. Their first demand will be "give me money/tech or I will squash you", you cave in, and then they're like "ha, you're begging for mercy, give me more". That is why I always stand up to AIs on their stupid demands or pick the make trade option if it is available. The best way to defend one city base would involve: 1. Forests, followed by bunkers when you get the tech; 2. sensors; 3. up to date on metal defence tech; 4. strong rovers to destroy stacks; and 5. Good support mechanics going to clean reactors. Going green and getting mind worms for free helps but never, ever return your mind worms to base, because then they cost upkeep from your base.