This hadith (see here) has some interesting lessons one could learn:
The sahahbi 'Aidh ibn 'Amr عَائِذَ بْنَ عَمْرٍو visited the actual governer of Basra 'Obaydallah ibn Ziyad عُبَيْدِ اللَّهِ بْنِ زِيَادٍ and gave him an advice based on a statement he heard from the prophet():
The worst of guardians is the cruel ruler.
with the additional advice:
Beware, Don't be one of them!
Ibn Ziyad apparently disliked hearing this advice and considered it as disrespect from this man who is a sahabi, but not a much known one and said:
"Sit down, you are but husk from among the Companions of the Prophet (PBUH)."
Husk here might be a rather bad translation as what he was referring to is نخالة which is the bran not the husk, and this expression in Arabic means from "the worst part of a thing".
Even in fact in some places and countries it is even considered the total opposite (sometimes Arabs use the opposite word to express a thing). I even once heard a scholar explaining the hadith the other way around, but I guess he was not aware about the two involved individuals of this narration, as he only quoted the content!
Now in fact 'Aidh ibn 'Amr who certainly is a sahabi, but is not famous for his knowledge of the qur'an, sunnah or tafsir etc. as there are certainly other names that come easier to mind. But the governor of the the Caliph Yazid ibn Mu'awiya ibn abi Sufyan wanted to order this sahabi to sit down and shut up (Ibn Ziyad became governor 55 a.H. and was only 22 years old he was the leader of the army that killed al-Hussain ibn 'Ali the grandson of the prophet and was later killed by Ibrahim ibn al-Ashtar an-Nakha'i).
'Aidh ibn 'Amr who was among those who witnessed the baya'a of al-'Aqabah was a much older man who has learnt to speak the truth even in front of a oppressive ruler (see for example in Sunan abi Dawod) and that sincerity and well wishing is part of the religion (See for example in Sahih Muslim) and answered:
"Was there any husk among them? Surely, husk came after them and among others than them".
which means when it comes to privilege of having met the prophet () or learnt from him and gained knowledge of the Qur'an and sunnah all the sahabah are the same, while later generations may or may not gain this knowledge depending on their opportunities.
So far this is my long explanation of this hadith based on my own understanding and some the historical circumstances of this meeting.
From the commentary of imam an-Nawawi
Imam an-Nawawi in his commentary on Sahih Muslim -see here in Arabic- concentrated on the content of the hadith saying:
In the following I will translate from Arabic, as this translation is of my own take it carefully!
قوله : ( إنما أنت من نخالتهم ) يعني : لست من فضلائهم وعلمائهم وأهل المراتب منهم ، بل من سقطهم ، والنخالة هنا استعارة من نخالة الدقيق ، وهي قشوره.
(you are but husk from among them) means: you are not among the noblest among them, nor the scholars among them, nor those of a high rank among them, but among the insignificant among them. The husk/bran here is a metaphor from the husk of flour, which is it's shell
قوله : ( وهل كانت لهم نخالة ؟ إنما كانت النخالة بعدهم وفي غيرهم ) هذا من جزل الكلام وفصيحه وصدقه الذي ينقاد له كل مسلم ، فإن الصحابة - رضي الله عنهم كلهم - هم صفوة الناس وسادات الأمة ، وأفضل ممن بعدهم ، وكلهم عدول ، قدوة لا نخالة فيهم ، وإنما جاء التخليط ممن بعدهم ، وفيمن بعدهم كانت النخالة .
("Was there any husk among them? Surely, husk came after them and among others than them") this is a part of clear, truthful and eloquent speech which every Muslim should abase himself before. As the sahabah -may Allah be pleased with all of them- are the cream of the people and the sovereigns of this ummah, and better than those who followed them, and all of them are trustworthy, and guidance and there's no husk/bran among them, but the mixing (of both) came afterwards and afterwards there was the husk/bran.
قوله صلى الله عليه وسلم : إن شر الرعاء الحطمة قالوا : هو العنيف في رعيته لا يرفق بها في سوقها ومرعاها ، بل يحطمها في ذلك وفي سقيها وغيره ، ويزحم بعضها ببعض بحيث يؤذيها ويحطمها .
The statement of him Allah's prayers and Blessings be upon him: "The worst of guardians is the cruel ruler" means the ruler who is harsh and violent with his citizens and is not kind to them in their markets and in his rulings, but hurts and oppresses them in this and in the watering etc. and is pushing some of the citizens against others to harm them and break them (break the solidarity between citizens).