ISO of a dog lover/trainer. This is my dog Loki, he's a black lab/border collie mix. This is my problem: He's extremely scared of strangers. He hasn't been socialized properly. He's such a sweet smart dog, but he shows aggressive behavior towards strangers. It is to the point where we can't have company without locking him in his kennel, and the whole time he's in the kennel he barks and growls the whole time. Sometimes he even defecates and urinates in the kennel because he gets so worked up. I don't know how to socialize him now because I'm terrified to introduce him to new people. Can anyone help me?