In The Name of Allaah, The Most Merciful The Bestower of Mercy.
Allaah [The Most High] said:
وَإِذَا قِيلَ لَهُمۡ لَا تُفۡسِدُواْ فِى ٱلۡأَرۡضِ قَالُوٓاْ إِنَّمَا نَحۡنُ مُصۡلِحُونَ
أَلَآ إِنَّهُمۡ هُمُ ٱلۡمُفۡسِدُونَ وَلَـٰكِن لَّا يَشۡعُرُونَ
وَإِذَا قِيلَ لَهُمۡ ءَامِنُواْ كَمَآ ءَامَنَ ٱلنَّاسُ قَالُوٓاْ أَنُؤۡمِنُ كَمَآ ءَامَنَ ٱلسُّفَهَآءُۗ أَلَآ إِنَّهُمۡ هُمُ ٱلسُّفَهَآءُ وَلَـٰكِن لَّا يَعۡلَمُونَ
And when it is said to them: ‘’Make not mischief on the earth,” they say: “We are only peacemakers. Verily! They are the ones who make mischief, but they perceive not. And when it is said to them [hypocrites]: ‘’Believe as the people [followers of Muhammad (sallal laahu alayhi wasallam) have believed,’’ they say: ‘’Shall we believe as the fools have believed?’’ Verily, they are the fools, but they know not. [Surah Al-Baqarah. Aayaat 11-13]
Imaam Ibnul Qayyim [rahimahullaah] said: This debate took place between the believers and the hypocrites; the believers said to them, ‘’Make not mischief on the earth’’; the hypocrites replied, ‘’We are only peacemakers.’’ So, it seemed as if the debate between the two partners has ended, and that the hypocrites have nullified the claims of the people of Eemaan that they are mischief makers and [proved] that peace making is what should be attributed to them instead of mischief making. So, Allaah [The All-Mighty, The All-Wise] passed a judgement between the two parties and established four proofs against the hypocrites.
Firstly: They are liars. Secondly: They are mischief makers. Thirdly: They are trapped in mischief making. Allaah said: [أَلَآ إِنَّهُمۡ هُمُ ٱلۡمُفۡسِدُونَ – Verily! They are the ones who make mischief]. Fourthly: Allaah described them as a people who are upon extreme ignorance and that they definitely do not possess [sound] perception due to the fact that they are mischief makers.
So, ponder upon the way in which perception was negated from them in this Aayah! Then knowledge was negated from them when Allaah [The Most High] stated that they said: [أَنُؤۡمِنُ كَمَآ ءَامَنَ ٱلسُّفَهَآءُۗ – Shall we believe as the fools have believed], so Allaah [The Most High] said: [أَلَآ إِنَّهُمۡ هُمُ ٱلسُّفَهَآءُ وَلَـٰكِن لَّا يَعۡلَمُونَ -verily, they are the fools, but they know not].
Allaah [The Most High] negated knowledge from them due to their foolishness and lack of [sound] perception -a severe dispraise and [declaration] of their ignorance, because [of the fact that although one is truly] a mischief maker, [however he] is completely unaware of it, even though its effects is well known and witnessed by Allaah’s slaves. This shows the severe corruption of one’s intellect and sources of knowledge.
Also, he is a foolish person and foolishness is the height of ignorance, which occurs due to lack of knowledge of that which benefits him in his worldly life, his afterlife, his purpose [of life] and what is contrary to that. So, when he [finds] himself in this situation, whilst being unaware of his state of affairs, then this is the most wretched state of a human being.
[Sound] knowledge was negated from him due to his foolishness, which of a surety is an affirmation of his ignorance; [and sound] perception was negated from him due to the mischief making, which of a surety is due to corruption in his mental faculties. Therefore, these three verses are statements of absolute certainty against them regarding their ignorance and corrupt mental faculties, because they believe that mischief making is peace making and that evil is something good.
Source: An Excerpt from ‘Badaa-i at-Tafseer Al-Jaami Limaa Fassarahu Al-Imaam Ibnul Qayyim. Vol 1. page 97. Slightly paraphrased