Shaykh Ibn Abd al-Wahhaab (rahimahullaah) said in (مجموع مؤلفات الشيخ محمد بن عبد الوهاب), a collection of his works and writings, in his letter to Muhammad bin 'Eed (7/25):

As for what the enemies have mentioned about me: That I make takfir on the basis of presumption, and on the basis of loyalty, or that I make takfir of the ignorant person upon whom the proof has not been established, then this is a mighty slander. They desire to make the people flee from the deen of Allaah and His Messenger by it.

And Shaykh Ibn Abd al-Wahhaab also said (7/60):

And likewise, his distortion upon the common people that Ibn Abd al-Wahhaab says, "Whoever does not come under my obedience is a disbeliever." And we say: Sublime are you (O Lord), this is a mighty slander! Rather, we call Allaah to witness over what he knows from our hearts that whoever acts upon Tawhid and frees himself from Shirk and its people, then he is a Muslim in whatever time and place (he maybe in). But we make takfir of the one who associates partners with Allaah in His Ilaayhiyyah (sole right of worship), after we have made clear to him the proof for the futility of Shirk.

And Shaykh Ibn Abd al-Wahhaab said (in the section, Fataawaa wa Masaa'il, 4/11):

And as for the lie and slander, then it is like their saying that we make generalized takfir (of the masses), and that we make emigration (hijrah) obligatory towards us for the one who is able to manifest his religion, and that we make takfir of the one who does not make takfir and who does not fight, and multiple times the likes of this (type of lying and slander). All of this is from lying and slander by which they hinder the people from the deen of Allaah and His Messenger. And when it is the case that we do not make takfir of the one who worships the idol (i.e. tomb) which is on the grave of Abd al-Qadir, and the idol which is on the grave of Ahmad al-Badawi and their likes, due to their ignorance, and the absence of the one to notify them (of their opposition), then how could we make takfir of the one who does not associate partners with Allaah, when he does not emigrate to us and who does not make takfir and does not fight? "Glory be to you (O Lord), this is a mighty slander." (24:16)

And in al-Durar al-Saniyyah (10/131), there occurs the statement of Shaykh Ibn Abd al-Wahhaab in one of his letters;

What has been mentioned to you that I make generalized takfir (of the masses), this is from the slanders of the enemies. Likewise, their saying that I say whoever follows the deen of Allaah and His Messenger whilst resident in his own land, this is not sufficient until he comes (emigrates) to me. This is also from slandder. Rather, the intent is for [a person] to follow the deen of Allaah and His Messenger in whichever land it may be. However, we make takfir of the one who affirmed the deen of Allaah and His Messenger, then showed enmity towards it and prevented the people from (following) it. Likewise the one whow worships idols (awthaan) after he came to know that it is the deen of the pagans, and who then beautified it to the people. This is the one that I make takfir of, and every scholar on the facce of the earth makes takfir of (the likes of) these, except a stubborn opposer or an ignoramus.

Notes

Refer to the article from Shaykh Ibn Uthaymeen (rahimahullaah) for some further clarification. Shaykh al-Islam Muhammad bin Abd al-Wahhaab does not make takfir of those who fall into shirk except after the establishment of the proof, and the proof is established upon a person's mere realization that he is acting in opposition to the deen of the Messengers. He is not required to understand or fathom anything more or deeper than this. From here, he will a) ignore and not pursue the matter to remove himself from the ignorance and shubhah (doubt) that should have been generated by this realization (and this would be kufr of i'raad, turning away), or b) he may show opposition (juhood, inaad) or c) he may educate himself and abandon what he was upon, since he is seeking to follow the deen of Islaam and this was his intent all along, but he was simply misguided and the reality of the deen of the Messengers had not reached him or been explained to him.

Whatever the case, the person's actions were no doubt shirk and disbelief, but the actual ruling upon him that he is a disbeliever, is only made after establishment of the proof.

In all the above, one should also keep in mind that what counts as "known from the religion by necessity" (and therefore "establishment of the proof") fluctuates and varies according to time, place and person and is not a fixed, static thing. It is not to be said absolutely "an ignorant person is excused" and nor is it to be said absolutely "an ignorant person is not excused" but there is tafseel (detail to the matter). This topic will be taken up in other articles inshaa'Allaah.