Silkies are by nature gentle and sweet and are considered one of those breeds that are more prone to bullying. Their more limited eye sight plays a factor in this as well. Additionally, I've found BSL's and RSL's to be pretty aggressive, sometimes plain mean, to newbies. I had one who would get a younger bird in a corner and just go to town pecking the tar out of it. She (the sex-link) went to solitary confinement for a while. The best way to go about introducing new additions is the look-but-don't-touch method. Have the new bird(s) in something, like a cage, crate, or separate part of the coop, to where the flock can see it, but not get at it. I usually do this for a week, then let them out on free range together. That way they're on "neutral" ground. I monitor them very closely for a couple of days. If all goes well (a few pecks are to be expected), I'll set the new bird(s) on a low roost during the night while the others are asleep. Usually works well. If there are problems, the newbies go back into the caged part of the coop and I'll try again in a few days.
As the saying goes. "Birds of a feather, flock together".
Some birds do not like other birds with different feather, colour or type.
I had RIR Hens last year and they hated all my non red hens. I got rid of the reds.