The narration that is quoted states contains the following:
حدثنا عباس النرسي قال حدثنا عبد الواحد قال حدثنا ليث قال أخبرني رجل من أهل البصرة قال سمعت معقل بن يسار يقول : انطلقت مع أبي بكر الصديق رضي الله عنه إلى النبي صلى الله عليه و سلم فقال يا أبا بكر للشرك فيكم أخفى من دبيب النمل
maaqil bin yasar says that once i went along with abu bakar to holy prophet asws, and he asws said:- o abu bakar, shrikh is walking in you in tone which is silent than the walk of ant……
As anyone that reads the narration in Arabic can see, one of the narrators is referred to as a “man from the people of Basra”. This in itself is enough to reject the hadith due to the anonymity of the narrator.
Shias will argue that Al-Albani authenticated the narration in his Saheeh Al-Adab Al-Mufrad. This is because similar wordings have been used in other hadiths, like ones narrated by Abu Musa in Musnad Ahmad and Ibn Abbas in Tafseer Ibn Abi Hatim. In other words, Al-Albani arrived at the conclusion that some of the wordings of the narration is authentic. The other two wordings do not suggest that Abu Bakr is being referred to as one that has shirk within him, which is why we know for a fact that this is not authentic.