The Guide for the Perplexed answers your question and also the Raavad’s objection that many great and worthy people conceived of God corporeally. Here is the wording (Part I, chapter 36):
‘And if it occurs to you that one should find merit for those who believe in corporeality, because he was educated that way, or because of his ignorance and the limitation of his understanding, then you ought to hold the same view regarding an idol worshiper, since he worships only because of ignorance or upbringing, the customs of his fathers being in his hands. And if you say that the plain meaning of the verses led them into these confusions, know that the idol worshiper too was brought to his worship only by imaginings and defective notions. It follows that there is no excuse for one who does not rely on the true thinkers, if his own speculative ability is deficient. And I do not regard as a heretic one to whom the negation of corporeality has not been demonstrated, but I do regard as a heretic one who does not fix in his mind its negation, especially given the existence of the translation of Onkelos and the translation of Jonathan ben Uzziel, peace be upon them, which kept far away from corporeality to the utmost degree.’
So it is very hard to judge them favorably.

People tend to let things go in one ear and out the other.

You can judge them favorably quite easily, but that has nothing to do with the question of whether to pray with them.

And when I think about it, the Chabad people really do resemble the story of that fool who thought he was the messiah in the responsa Igrot Moshe (Even HaEzer 120), where Rabbi Moshe Feinstein permitted him to give a bill of divorce (taken from “Keren Zavit” by Nadav Shenarav). His reasoning was that since that fool kept it secret and behaved normally, this thought did not stem from an epistemic defect but from a moral defect, namely pride. Practically speaking, the Chabad people—if they believe these beliefs—keep it secret, and therefore the argument of Igrot Moshe applies to them.

As I wrote above, the discussion is not about whether they are of sound mind, nor about whether they are culpable (coerced, inadvertent, or deliberate). The question is whether they believe in the Holy One, blessed be He, and the answer is no. They are idol worshipers through association plus corporealizing God.

In my opinion, in most cases they can be counted for a minyan. This is because the Thirteen Principles of Faith have been accepted by most of the Jewish people, and they have supreme status. When a Chabad Hasid or a Breslover says that the Rebbe is God or something in that style, he does not really mean what he says; he is usually expressing intense feelings of attachment to the righteous leader and so on. But if you ask him, “Do you mean by your words to contradict the Thirteen Principles of Faith? If it is proven to you that your words about the divinity of the righteous leader contradict them, will you retract them?” usually they will answer that the Thirteen Principles have supreme status, and that the teachings of their rabbis and their beliefs must be interpreted accordingly.
That is to say, in the end the Chabad Hasid and the Breslover treat the Thirteen Principles as overriding principles, by which Hasidism must be interpreted. Therefore they are considered Jews who believe in the unity of God.