The Khawaarij are the mischief-makers:

بسم الله والحمد لله والصلاة والسلام على رسول الله ، وبعد

Do you know why in their history the Takfeeris/Khawaarij never got to rule the Muslim Lands?

Do you know that the Shias (Fatimids) and the Soofees ruled the Muslim lands, but the Khawaarij did not?

Do you know the reason why? It is because of their love for spreading mischief (Fasaad) on earth while they are thinking that they are peacemakers!

They make takfeer of the masses; they make it permissible to shed blood of the Muslims, they killed more Muslims than they ever killed the Kuffaar. The blood of the Sahaabah are on their hands including the elite of them the two Khaleefahs, `Uthamaan and `Alee رضي الله عنهما.They destroyed Muslim lives, their lands and their wealth. The Kuffar are safe from them but not the Muslims.

Allaah تعالى said:

﴿وَالصُّلْحُ خَيْرٌ﴾

{…and making peace is better} [Surah al-Nisaa’ (4): 128]

Shaikh al-Sa`dee رحمه الله said:

Pursuing to make peace between people is better than optional prayers, fasting and charity. For the peacemaker, no doubt Allaah تعالى will set right their quest and their actions (and will aid them).

But as for the quest for making mischief, Allaah does not set right their actions nor does He aid them in fulfilling their objectives as He تعالى said:

﴿إِنَّ اللَّهَ لا يُصْلِحُ عَمَلَ الْمُفْسِدِينَ﴾

{Verily, Allah does not set right the work of Al-Mufsidoon} [Surah Yunus (10): 81]

---end of quote from Tafseer al-Sa`dee (4): 114

Moreover Allaah تعالى said:

﴿وَاللَّـهُ لَا يُحِبُّ الْفَسَادَ﴾

{Allaah likes not mischief} [Surah al-Baqarah (2):205]

﴿إِنَّ اللَّـهَ لَا يُحِبُّ الْمُفْسِدِينَ﴾

{Allaah likes not the Mufsidoon (mischief-makers)} [Surah al-Qasas (28): 77]

﴿وَلَا تَتَّبِعْ سَبِيلَ الْمُفْسِدِينَ﴾

{…and follow not the way of the Mufsidoon.} [Surah al-A`raaf (7): 142]