Is one excused for ignorance if he calls upon other than Allah?

The Shaykh : He says: What is your opinion regarding one who calls upon a wali (close friend of Allah) or someone else other than Allah, and he does not know that this is shirk (associating partners with Allah)? Is he living among Muslims, or is he in a place far from Islam and tawhid (the oneness of Allah)? If he is far from Islam and tawhid, then he is excused for his ignorance, unless he is negligent in seeking knowledge. But if he is living among Muslims, then the matter is clear; he is a mushrik (one who associates partners with Allah) and is not excused. And this is Umm Abdullah.