Then I have to ask... what's the point? Why is the option taking up valuale memory?
Like already said, it's not necessarily for single player games, as it has more value in a multiplayer game ... but that's true of tech trading as well. You do a "I'll give you Theology now if you give me civil service later" kind of thing.
But even without diplomatic bonuses, protecting a neighbor is enough. Think of gifting units as a permanent alliance without the permanence or public knowledge. When you have a weak Ghandi standing between you and a strong Monte, you'll know that setting a dozen marines to help out Ghandi's musketmen makes a big difference. And then Monte doesn't even know that you've helped his enemy, keeping you from gettting a diplomatic negative!
This makes it a good "covert partner" strategy. Say you want Asoka dead, but in the meantime, Asoka is hooking you up with good luxury trades, or is best friends with Catherine, who is your best buddy, a relationship you hope to turn into a Def Pact later in the game. Now, when Tokugawa declares on Asoka, you're giddy, but helping him out with cash donations or a gift of Iron (or some other important resource) will make Asoka dislike you ... an effect that might rub off on Cathy. So instead you have a short-term Open Borders with Toku, throw a dozen Calvary and a few riflemen and a handful of cannons his way, and let the sparks fly. When Asoka asks you to quit your deals with Toku, you can, because you've already given him the ammunition to take a few cities ... and Asoka is none the wiser that he's bleeding out of both holes because of your assistance.
Politics is a beautiful thing!
