In The Crucible what does Proctor mean when he says, ''keep it from such dogs''? ''For now I do think I see some shred of goodness in John...

The "dogs" that Proctor is referring to in this quote are
all of the judges and court officials who keep trying to get him to confess to the sin
of witchcraft.  He is not guilty of witchcraft--he knows this, and anyone who knows him
knows this--and yet, the courts and judges insist, based on the testimony of the
cowardly Marry Warren, that he is in fact a witch.  They bother him constantly, wanting
him to confess; they think that if John confesses, that will motivate others who are
holding out to also confess.  The more people that confess means the more that the
courts are proven right in their accusations of witchcraft (which inflates their pride
and makes them look wise and all-knowing).  Also, if more people confess, that means
fewer people hang; at this point, the townspeople are starting to get angry about the
hangings, so the courts are wanting to cut down on that.  They feel that John's
confession is key in helping others to also confess.

So,
Proctor calling them dogs is just a reflection of how he feels about them; he feels the
judges are immoral, foolish, evil creatures who are power-hungry, greedy men bent on
making good people do bad things.  He hates them, and so calls them dogs, and refuses to
do what they want him to, which is confess to witchcraft.  He concludes that he is
indeed a good man, and that he can see that for himself now.  Even though the dogs that
arrested him and are about to hang him don't see him as a good man, he has finally come
to see "a shred of goodness" in his character, through his refusal to
confess.

I hope that helped; good
luck!