Taking from an innovator who specialises in a particular field? | Shaykh Ibn al-Uthaymeen

Shaykh Muhammad Ibn Saalih Al-‘Uthaymeen (rahimahuAllah) mentioned in his explanation of ‘Hilyatu Talab Al- ‘ilm’ by Bakr Abu Zayd on the following statement: “It was narrated that (Imaam) Maalik -rahimahuAllah- said: “Knowledge is not taken from four: a foolish person who publicises his foolishness, even if he was the most prolific narrator of hadeeth; a person of innovation who calls to it; a person who lies in the speech of the people, even if I don’t accuse him (of lying) in hadeeth, and a noble, pious worshipper if he does not memories precisely what he narrates.” [As-Siyar, (8/61)] (Shaykh Bakr Abu Zayd): So O you seeker of knowledge, if you are in a position of freedom of choice then do not take from a mubtadi’ (innovator); whether he be a Raafidhi, Kharaji, Muriji, Qadaree or Qubooree….etc. For you will never reach the level of (knowledgeable) men: correct in creed, strong in your association with Allaah, with strong vision, and following the tracks; except by abandoning the mubtadi’ah and their innovations.
Shaykh Muhammad Ibn Saalih Al-Uthaymeen said explaining the above statement: “And that which is apparent from the statement of the Shaykh (Bakr Abu Zayd) is that no knowledge is taken from the mubtadi’ even if it’s in something that is not in relation to his innovation. So for example, if we were to find a mubtadi’ that is proficient in the Arabic language; al-Balagha, an-Nahw, as-Sarf – do we sit with him and take knowledge from him in that which he is proficient in or do we boycott him? What is apparent from the statement of the shaykh (Bakr Abu Zayd) is that we don’t sit with him because this imposes two evils:
The first evil: He (the mubtadi’) deceives himself (to an extent) that he thinks he is upon the truth.
The second evil: The people being deceived by him which causes the people and the students of knowledge to follow (the mubtadi’) and take knowledge from him. Whilst the general layman is unable to differentiate between ‘ilm an-Nahw (the knowledge of Arabic grammar which he the mubtadi’ is proficient in) and the ilm al-‘aqeedah.
Due to this, I see that a person should not sit with the people of innovation/desires completely, even if one does not find the knowledge of the Arabic Language, al-Balagha and as-Sarf expect amongst them, for indeed Allaah will bring about someone even better than them. However, for us to simply go to them (the people on innovation) frequently will cause them to become deluded by themselves, and the people to be deceived (and misled) by them.”
(Shaykh Ibn ‘Uthaymeen went on to mention): “The author (Sh. Bakr Abu Zayd) warned against the people of innovation a great warning, and they are deserving of this. Particularly if the mubtadi’ is (persuasive and) eloquent in speech, because his evil will be more greater.”