Chickens will be chickens. They need to establish their pecking order to have peace. I just integrated three silkies into my run with 5 regular sized pullets. but they are 8 weeks younger, so they don't get to free range with the 15 week olds.I started with putting two silkies in, and then one week later added a third. Since they are bantams and sooo much smaller, I was worried they would just get trampled. for the first three days, I had them in a pen inside the run, so they can familiarize with each other. Then I let the big girls into the pen, one at a time. I supervised the interactions, just incase something got out of hand, but didn't actually need to intervene in the end, they all got their pecks in and no one was worse for wear. In the end first my paint silkie mix got the most picked on, so you would think she wouldn't pick on others right? wrong! I brought in a new black silkie the following week, they were actually brood mates before. Once the new comer was in the pen, paint pecked the heck out of new silkie! It's been three days now, and all has settled down save for the occasional peck. I leave them to sort it out, as long as they have full crops and are active, I don't worry about bullying, or try to intervene. Chickens are not people, they do things that don't make sense to us, but for them it's necessary and instinctual.
Here's a video of paint silkie mix being pecked. The BSL doesn't actually peck very hard, these birds are just good at being drama queens

She still gets pecked on by one russian orloff, who is at the bottom of the pecking order. I read that the birds who are at the bottom are usually the most vicious to new comers, so it does make sense.