I don't like the redlined stuff. Even if they hate you, they'll gladly accept any of your technologies, but refuse to give anything of theirs.
I've been offered a mediocre tech for several good techs of mine before by the AI, so I choose "Care to negotiate?". As soon as I hit the option the item they offered 2 seconds ago is redlined!! This annoys me, as they AI is clearly willing to give it away if it got a good bargain. So, now even if you wanted to offer even MORE for the tech, they refuse point blank.
I really wish you could really persuade AIs into deals. Having many many redline items makes diplomacy so unfun. Sure some could abuse the AI that way, but I just play for fun, not to ruthlessly exploit the AI to biggest extent possible.
I'd just like more realistic deals.
As for giving away cities, the AI will happily plonk a city in the middle of a frozen wasteland of glaciers, it probably doesn't analyze it's quality? Maybe just size? or perhaps it all goes down to just attitude towards you.