Shaykh Abdul-Maalik Ar-Ramadaani said, “Whoever finds in this research of mine anything from harshness, then let him not get carried away and say things like, “He speaks about his brothers and is silent about his enemies (i.e. the disbelievers).”
So let it be known that the basic principle in enjoining the good and prohibiting the evil is gentleness and kindness, as Allaah the Exalted said, “Call to the Way of your Lord with wisdom and a good admonition, and debate with them in a manner that is good.” [Sooratun-Nahl 16:125]
And He said to Moosaa and Haaroon (may the Prayers and Peace of Allaah be upon them both), “Go to Fir’awn, for verily he has transgressed. So speak to him a gentle word, perhaps he may remember or fear.” [Soorah Taa-Haa 20:43-44]
The Prophet (sallallaahu ‘alayhi wa sallam) said, “Gentleness is not found in something, except that it beautifies it. And gentleness is not taken out of something, except that it disgraces it.” 
So if an evil cannot be averted, except with a type of roughness, then there is no problem in utilizing it – even if it be with Muslims.
Do you not see that Allaah permitted fighting [in a certain circumstance between believers] and harshness [towards another Muslim for Allahs sake] is not worse than fighting [him for Allahs sake].
So Allaah the Glorified said, “And if two groups from the Believers fight, then reconcile between them. So if one of them oppresses the other, then fight the one that commits oppression until it returns to the Command of Allaah.” [Sooratul-Hujuraat 49:9]
So the believer must be much more severe in harshness towards his brother [that doesn’t mean he is to rude to his brother or insults him], than towards the enemies of his brother; do you not see that Moosaa (‘alayhis salaam) was gentle with Fir’awn, and harsh upon his own brother Haaroon (‘alayhis salaam), to the extent that Allaah the Exalted related about him, “And he took his brother by the head, and pulled him towards him…” [Sooratul-A’raaf 7:150]
So can anyone dispute with him concerning al-walaa wal-baraa (allegiance and enmity), accusing him of raising his hand and tongue against his brother and being nice to the tawaagheet (false gods)?! Never!
Rather, the Prophet (sallallaahu ‘alayhi wa sallam) was much more severe with the scholars from his companions, than he was with other than them.
Take as an example his statement to Mu’aadh, when he lengthened the Prayer with the people, “Are you a person who causes fitnah (trouble), O Mu’aadh?” 
This comes along with his (sallallaahu ‘alayhi wa sallam) gentleness to the Bedouin who urinated in the mosque, as is reported in Saheehul-Bukhaaree and others. 
He (sallallaahu ‘alayhi wa sallam) also said to Usaamah Ibn Zayd (radiyallaahu ‘anhu), when he was fighting a disbeliever in the battlefield who had just uttered the word of Tawheed, “O Usaamah! Do you fight him after he has said that there is no deity worthy of worship besides Allaah?!!”
Usaamah said, “So I did not cease repeating it (i.e. the testification of faith), until I was no longer certain that I had accepted Islaam before that day.” 
Indeed Usaamah benefited from this harshness in advising, during the days of fitnah (trials/tribulations) that occurred after the murder of Uthmaan (radiyallaahu ‘anhu). So he stayed away from spilling the blood of the Muslims.
Imaam adh-Dhahabee (d.784H) – rahimahullaah – said, “So Usaamah benefited since that day with the Prophet (sallallaahu ‘alayhi wa sallam) when he said, ‘O Usaamah!?’ So he stopped his hand and remained in his house, and thus attained good.” 
I say, how magnificent is the Prophetic education!
[On the other hand] how wretched is the education of hizbiyyah (party-spirit) which has prohibited the principle of ar-radd ‘alal-mukhaalif (refuting the opponent to the truth)…
Ibn Taymiyyah (d.728H) – rahimahullaah – said, “The believer to the believer is like two hands, one of them washing the other and indeed the dirt cannot be removed, except by some form of coarseness. So cleanliness and softness only comes about by obligating that initial roughness.” 
Therefore, this [overly] gentle approach which is used by many of these Islaamic jamaa’aat (parties, sects) with the [misguided] individuals and [astray] groups, who are from the most light-headed of idiots [is completely wrong] – and the reason for this gentleness towards many of them [the misguided individuals and astray groups] is a serious lack of not having enmity towards [the people of innovation] the enemies of the Muslims [although they themselves are Muslims they are referred to as enemies of the Muslims due to their leading Muslims away from the straight path and guiding them towards the paths of deviance and innovation].
[This action – being gentle and kind to astray groups and misguided individuals at all times under all circumstances] does not even have anything to do with walaa (allegiance) [to the misguided individual or astray group].
[Also this action] drowns them [the misguided groups; the astray individuals and the groups/individuals being overly gentle towards them at all times in all circumstances] further in their misguidance, due to them not realizing the greatness of their crime.
Then verily the motive behind traversing a path of harshness with the Muslims sometimes, is to bestow a sense of honour (gheerah) upon them from the foolish people who relate rubbish to them [making them think the way of truth is being gentle with misguided individuals and astray groups in every case and in all circumstances].
[So this harshness] is an attempt to strengthen the ranks [of the Muslims], and to stop rifts in Islam…”
 Related by Muslim (16/146)
 Related by al-Bukhaaree (1/669)
 Related by al-Bukhaaree (1/219)
 Saheeh: Related by at-Tiyaalisee and al-Bazzaar; it was authenticated by Shaykh al-Albaanee in Saheehul-Jaami’ (no. 7846).
 Siyar A’laamun-Nubalaa (2/500)
 Majmoo’ul-Fataawaa (28/53-54)
Ref: troid.ca via Maktabah-al-Fawaaid [with a few changes for easier reading by ahlusunnahwaljamaah.com]
Posted by Abdul Kareem Ibn Ozzie