What does Sherlock Holmes literally mean by telling Dr. Watson, "If they are guilty we should be giving up all chance of bringing it home to them"?

He simply wants to say that they should quit.

Explanation:

It's like this because if somenone is guily there's no need to try to bring this person home or make te person happy again, get the person back to its origin.

He doesn't want to give the suspect the chance to flee before justice can be served.