Itty bitty bantams VS my large chickens

They probably have a better chance out of the coop. I have bantams also and they chase the LF. I won't clip their wings. Hawks love bantams. Mine have gotten away from hawks being able Flo fly.

I've kept small bantam White Leghorns with standard hens for years. There's a few things to do to make it nicer for everyone. First is that the banties like a hiding place. I have the nesting boxes low enough that they can scoot under, but the big birds can't follow. It's where the little ones hang out during bad weather. Have outside roosts in the pen so that they all have space and some can get up off the ground. Feed treats in several places. Have plenty of space! They'll need a minimum of 4 feet interior coop space, and another 8 outside PER hen. If possible, add a second feeder. That should do it, and peace will prevail :)

My banty hens (and a couple of roosters) are perfectly fine in the flock and coop, but I do have a lot of space for them. They also grew up in the flock... Did you segregate them first, someplace they were able to see and hear each other for a couple of weeks before letting them in with everyone else? I find that helps; just a separate place in the coop, divided off by chicken wire.

I don't clip anybody's wings for the same reason as already mentioned. Flying is a way for them to protect themselves.

I have a barn filled with bantams and a couple of standard hens. Because the large hens were introduced to the bantam flock, the bantams were the "alpha" chickens and they picked on the big girls! It's hilarious to see a tiny bantam hen chase a big cochin hen.

 

If you are introducing bantams to a flock of standard chickens, however, it will be the opposite - as you've already found out. In your case, it probably would be best to give the bantams their own secure coop (secure from predators -- use heavy, stiff hardware cloth wire with smallish holes to keep raccoon paws out; make sure the coop is set in the ground in a way that foxes and skunks can't burrow under and in, cover the top so hawks and other raptors and climbing raccoons and oppossums can't get in, and give them a good weatherproof shelter with roosts).

 

I would not clip their wings since flying is their only defense!

When they are raised together bantams and standard fowl can generally coexist quite well.  When introducing birds to an established flock there are always pecking order problems.  When there is a significant size difference those problems become far more serious.  Yes, it is quite possible that your present flock may kill the new bantams.