I looked up the word "Kafir and found the following definition at Wikipedia. Is it correct?
Types of Kufr (Disbelief)-Adapted from 'Tafseer ibn Katheer[3] The Qur'an uses the word kufr to denote a person who covers up or hides realities, one who refuses to accept the dominion and authority of Allāh. There are several types of Al-Kufr ul Akbar:
1. Kufrul-'Inaad: Disbelief out of stubbornness. This applies to someone who knows the truth and admits to knowing the truth and admits to knowing it with his tongue, but refuses to accept it and refrains from making a declaration. The Qur'an states: "Do ye twain hurl to hell each rebel ingrate?" [Soorah Qaaf (50), Ayah 24] [4]
2. Kufrul-Inkaar: Disbelief out of denial. This applies to someone who denies with both heart and tongue. The Qur'an states: "They recognize the favor of Allah, yet they deny it, and most of them are ungrateful."[Soorah Nahl (16), Ayah 83] [5]
3. Kufrul-Kibr: Disbelief out of arrogance and pride. The disbelief by the devil (Iblees) is an example of this type of Kufr.
4. Kufrul-Juhood: Disbelief out of rejection. This applies to someone who acknowledges the truth in his heart, but rejects it with his tongue. This types of kufr is applicable to those who calls themselves Muslims but who reject any necessary and accepted norms of Islam such as Salaat and Zakat. The Qur'an states: "And they denied them, though their souls acknowledged them, for spite and arrogance. Then see the nature of the consequence for the wrong-doers!" [Soorah Naml (27), Ayah 14][6]
5. Kufrul-Nifaaq: Disbelief out of hypocrisy. This applies to someone who pretends to be a believer but conceals his disbelief. Such a person is called a MUNAFIQ or hypocrite. The Qur'an states: "The Hypocrites will be in the lowest depths of the Fire: no helper wilt thou find for them." [Soorah An Nisaa (4), Ayah 145] [7]
6. Kufrul-Istihlaal: Disbelief out of trying to make HARAM into HALAL. This applies to someone who accepts as lawful (Halal) that which Allah has made unlawful (Haram) like alcohol or adultery. Only Allah has the prerogative to make things Halal and Haram and those who seek to interfere with His right are like rivals to Him and therefore fall outside the boundaries of faith.
7. Kufrul-Kurh: Disbelief out of detesting any of Allah's commands. The Qur'an states: "And those who disbelieve, perdition is for them, and He will make their actions vain; That is because they are averse to that which Allah hath revealed, therefor maketh He their actions fruitless."[Soorah Muhammed (47), Ayah 8-9] [8]
8. Kufrul-Istihzaa: Disbelief due to mockery and derision. The Qur'an states: "And if thou ask them (O Muhammad) they will say: We did but talk and jest. Say: Was it at Allah and His revelations and His messenger that ye did scoff; Make no excuse. Ye have disbelieved after your (confession of) belief. If We forgive a party of you, a party of you We shall punish because they have been guilty." [Soorah Taubah (9), ayah 65-66] [9]
9. Kufrul-I'raadh: Disbelief due to avoidance. This applies to those who turn away and avoid the truth. The Qur'an states: "And who is more unjust than he who is reminded of the communications of his Lord, then he turns away from them and forgets what his two hands have sent before? Surely We have placed veils over their hearts lest they should understand it and a heaviness in their ears; and if you call them to the guidance (Qur'an), they will not ever follow the right course (Islam) in that case." [Soorah Kahf (18), Ayah 57] [10]
10. Kufrul-Istibdaal: Disbelief because of trying to substitute Allah's Laws. This could take the form of: (a) Rejection of Allah's law (Sharee'ah) without denying it, (b) denial of Allah's law and therefore rejecting it, or (c) Substituting Allah's laws with "artificial" (i.e. non-Muslim) laws. The Qur'an states: "And if Allah had pleased He would surely have made them a single community, but He makes whom He pleases enter into His mercy, and the unjust it is that shall have no guardian or helper." [Soorah Shuraa(42), Ayah 8] [11] The Qur'an says: "Truly, Allâh is with those who fear Him (keep their duty unto Him), and those who are doers of good and righteousness." [Soorah Nahl (16), Ayah 116] [12]
My point is that it is always safest to avoid that of which there is doubt. And, it is always wise to follow the learned. However, unless someone states that which is in direct opposition to Al Qur'an or Strong Authentic Hadith it is dangerous to label that person as one to be avoided. I know that no one has called this person a karif and merely warned against accepting him as a Scholar. So, the following is not directed at anyone.
According to the Quran, if a person says assalamu alaikum to us to indicate that he is a Muslim, we cannot say to him ``you are not a believer.'' (4:94)
``Ibn Umar related that the Holy Prophet said: If a Muslim calls another kafir, then if he is a kafir let it be so; otherwise, he [the caller] is himself a kafir.''
(Abu Dawud, Book of Sunna, edition published by Quran Mahal, Karachi, vol. iii, p. 484)
``Abu Zarr reported that the Holy Prophet said: No man accuses another man of being a sinner, or of being a kafir, but it reflects back on him if the other is not as he called him.''
(Bukhari, Book of Ethics; Book 78, ch. 44)
``Withhold [your tongues] from those who say `There is no god but Allah' --- do not call them kafir. Whoever calls a reciter of `There is no god but Allah' as a kafir, is nearer to being a kafir himself.''
(Tabarani, reported from Ibn Umar)
I, personally, strongly condemned the widely prevailing practice of takfir (i.e. one Muslim calling another kafir on grounds of some difference of religious belief or practice), which is common among religious leaders. The Roman Catholic Church had the history of oppressing any opposing view.
Fox's Book of Martyrs