answer: #Person2# has a high opinion of a guy and trusts him, but #Person1# thinks he is a sly dog.
documents: #Person1#: It sounds that you have a high opinion of him.
  #Person2#: He is an all-right guy. I have no bone to pick with him.
  #Person1#: Birds of feather flock together.
  #Person2#: But he is not a fine wether friend who could sell you down the river.
  #Person1#: You cannot judge a person that way. I have a hunch that he is a sly dog.
  #Person2#: Depends on with whom. He may be doing things on the sly, but he is honest with me. I trust him.
  #Person1#: You can never tell. He might do you in when he sees an angle in doing it.