Why did Morris only trust Mc Murdo to open his secrets?

McMurdo kept secrets for Morris before.

“I can’t forget that I spoke my heart to you once, and that you kept it to yourself, even though the Boss himself came to ask you about it.”

Morris had trusted Mc Murdo and considered him a secret keeper even for the first time, but why would he do that? Morris was quite aware about all the scowreres.They were cold hearted, ruthless, and inemotional. He knew that if he would share his secrets with anybody else. They would probably shoot him right away, but when it comes to Mc Murdo, it was different. As for Mc Murdo, Morris knew that he is new to this notorious gang of scowrers and he might not be as unkind and inemotional as the others in the gang. Trusting his thoughts, he poured out his helplessness and compulsion. He also told Mc Murdo about his true feelings and thoughts about the gang. Morris also revealed his past. He might have not been confident but when he knew that Mc Murdo didn't remove Morris's facade and made himself a trustworthy for Morris, he was glad that he chose Mc Murdo and so he could only trust Mc Murdo for his secrets.