Read the story.
The rightful King (Richard) went abroad on crusade. His brother (John) usurped power, raised taxes illegally for his own use, and got his friends, including the infamous Sherrif of Nottingham, to collect the money for him. Those friends collected for the King, plus a cut for themselves, all totally outside the law. This is not the same as lawful taxation; it was extortion. John is not a lawful tax gatherer, he is a thief. He does not have the authority to raise the levels of taxation, and his friends did not have the authority to steal more on top.
Robin of Loxley objected, and as a result his lands and property was taken from him, and he was declared an outlaw. He went into the forest to live with the other outlaws, who, inter alia, ambushed those carrying the extorted money to the thieves. They took the money and gave it back to those who had been robbed of everything they had, and who had no means of living left to them.
Meanwhile the King had been captured, and an immense ransom asked for. His brother, who had no reason to pay this ransom and lose his power, refused to pay it. Robin went to the poor of the land, and asked them to give what they could. Between them they raised the necessary ransom, sent it abroad and the King was released.
When the King returned he pardoned Robin and the outlaws for any crimes they might have committed, and restored Robin's lands to him. He stopped the unfair taxation levels, set more reasonable taxes, and made sure the thieving stopped.
Therefore there is no question; according to the story Robin was a good guy.