Al-Fudail (rahimahullaah) said: “The believer conceals (the sin of his brother) and advises (him), while the evildoer disgraces and condemns (him).”
This is what Al-Fudail has mentioned as being from the signs of advising and condemning – and it is that advising is linked to secrecy while condemning is linked to publicizing.
It used to be said: “Whosoever commands his brother (towards doing good) at the head of a gathering, then he has condemned him.” Or it is something with this meaning.
The Salaf used to hate that commanding good and forbidding evil be done in this manner. Instead, they loved that it be done privately between the one commanding and the one being commanded, for indeed, this is from the signs of sincere advice.
This is since it is not the goal of the one who is advising to spread and publicize the faults of the person he is advising, rather his goal is only to put an end to the evil that he has fallen into.
As for spreading and exposing someone’s faults, then that is from the things that Allaah and His Messenger صلى الله عليه وسلم have forbidden. Allaah, may He be Exalted, says:
“Verily, those who love that the evil and indecent actions of those who believe should be propagated (and spread), they will have a painful torment in this world and the Hereafter. And Allaah knows and you know not. And had it not been for the grace of Allaah and His mercy on you, (Allaah would have hastened the punishment on you) and that Allaah is full of kindness, Most Merciful.” [Surah An-Noor: 19-20]
The ahaadeeth concerning the virtue of keeping the faults of others secret are many. Some of the scholars would say to those who were commanding towards good:
“Strive hard to conceal the faults of the sinners, for indeed, exposing their faults shows a weakness in Islaam. The thing that deserves the most to be concealed is one’s faults.”
It is for this reason that spreading someone’s evil and indecent actions is linked to condemning. And they are both from the affairs of the evildoer, since it is not the goal of the evildoer to put an end to the fault nor that the believer avoids that fault or defect. Rather his only goal is to spread and publicize the defects found in his believing brother, and to destroy his honor. So he initiates that and repeats it. And his intention is to belittle his believing brother by exposing his defects and bad qualities to the people so that some harm can fall upon him in this world.
But as for the person that is sincerely advising, his aim in doing that (advising) is to eradicate the faults found in his believing brother and to help him avoid it. This is what Allaah the Most High, has described His Messenger صلى الله عليه وسلم with, saying:
“Verily, there has come unto you a Messenger from amongst yourselves. It grieves him that you should receive any harm or difficulty. He is anxious over you (to rid you of faults and sin), for the believers he is full of pity, kind and merciful.” [Surah At-Tawbah: 128]
And He described his صلى الله عليه وسلم Companions with that, saying:
“Muhammad is the Messenger of Allaah. And those who are with him (i.e. his Companions) are severe with the disbelievers and merciful towards one another.” [Surah Al-Fath: 29]
And He described the believers with the characteristics of patience and mutual advising of one another towards mercy and compassion. 
But what drives the evildoer to propagate (his brother’s) evil and to disgrace him is force and harshness, his love for abusing his believing brother, and (his desire) to inflict some harm upon him. These are the characteristics of the Devil – the one who beautifies disbelief, sin and disobedience to the children of Aadam so that due to it they may become amongst the dwellers of the Hellfire, as Allaah says:
“Verily, the Devil is an enemy for you, so take him as an enemy. Verily, he only calls his party (of followers) to be from amongst the dwellers of the Hellfire.” [Surah Faatir: 6]
And He says, after telling us the story of Iblees (the Devil) when he was with the prophet of Allaah, Aadam, and the evil plot that he unleashed on him, such that it brought him to be cast out from Paradise:
“O Children of Aadam! Let not the Devil deceive you, as he got your parents out of Paradise, stripping them of their garments, to show them their private parts.” [Surah Al-A’araaf: 27]
So what a difference there is between one whose intention it is to advise (naseehah) and one whose intention it is to disgrace (fadeehah)! And no one confuses one of these with the other, except someone who does not possess sound intellect.
 See Fath-ul-Baaree (5/97) and Saheeh Muslim (4/1996)
 As is found in Allaah’s saying: “Then he became from among those who believed and recommended one another towards patience and recommended one another towards compassion.” [Surah Al-Balad. 17]
Source: From the al-ibaanah eBook :
The Difference between Advising and Condemning – Imaam Ibn Rajab