So two points:
1. 8 week old kittens are not capable of being aggressive. They don't have a mean or vicious bone in their body, they don't care about territory or the house pecking order, they simply have a really really high play need, as they are in "training to be a cat" mode. They need to gain strength, coordination, and practice all those predator moves that they would traditionally need to survive, and at 8 weeks, they quite frankly suck at all that stuff. They are certainly not a threat to anyone.
2. Older cats simply don't have the same needs as kittens do. So most of the time, the kitten's play advances are not going to be appreciated. You'd have to describe their encounters more carefully and precisely to really know what's going on, but you're older cat is definitely not socializing the kitten. He's either just telling the kitten: "eff off, leave me alone", or telling him: "this is my territory, I want you gone, you're not welcome here".
I think you definitely need to keep them apart for awhile (awhile probably means a week or two). And then when they do get back together, really carefully monitor and control their interactions. There's a lot of info around on how to do that (i.e., cat introductions) but the main challenge is to convince the older cat to accept the kitten as new resident of the home, as opposed to be an enemy.
I also don't really think that a cage is appropriate for a kitten of that age (if there is a proper age), and it's also going to be an impediment to getting the older cat to accept him. If you have a spare bedroom or something like that, that would be a lot better.
The little monsters 3