The Response of Shu'ayb's People
They said,
{O Shu'ayb! We do not understand} This means that we do not comprehend.
{much} 'most of what you say'. Ath-Thawri said, "He (Shu'ayb) was called the orator of the Prophets."
As-Suddi said,
{and we see you weak among us.} "They meant, 'You are only one person.'" Abu Rawq said, "They meant, 'You are despised, because your tribe is not upon your religion.'"
{Were it not for your family, you would have been stoned,}

This means, your people. Were it not for their powerful position over the people of Madyan, they would have stoned him to death. Some said that this means with rocks. It has also been said that this means that they would have cursed and insulted him verbally.
{and you are not powerful against us.}

This means, "You have no position of power over us."
Shu'ayb's Refutation of His People
{He said: "O my people! Is then my family of more weight with you than Allah?"}

He says: You would leave me alone out of respect for my people but not out of respect for the greatness of the Lord, the Most Blessed and Exalted? Does not your awe of Allah prevent you from harming His Prophet? Indeed you have placed the fear of Allah,
{behind your backs.}

This means that you have thrown it behind you. You do not obey it, nor do you respect it.
{Verily, my Lord is surrounding all that you do.}

This means that He knows all of your actions and He will reward you according to them.