Danzo is an important character to the Naruto Shippuden series in many ways whether he is hated or liked. There are many reasons to hate him and like him throughout the show, as shown below.

Danzo's actions:

•He came up with the idea to slaughter the Uchiha clan to save Konaha.

Tobirama, the second Hokage over watched and oppressed the Uchiha clan's self-governing district with the Konaha Military Police Force, originally designed to help the relationship between the Senju and the Uchiha, because he had a deep hatred for the Uchiha clan because their members killed many people in the Senju clan during a war between the two clans; he suspected them to try and regain power in Konaha.

This oppression only made the Uchiha clan hate the current Konaha even more, thus; engendering a coup d'état of Konaha from the Uchiha clan. The Uchiha's hate grew more and more towards Konaha throughout the years to were many suspected an Uchiha revolt of happen by the time of Hiruzen's, the 3rd Hokage's second reign shortly after Minato, the fourth Hokage died.

Itachi Uchiha was a double-spy during this time, working for Konaha's Anbu Black Ops. The Uchiha clan thought they could use Itachi as a means to gather information towards Konaha, but instead Itachi helped Konaha and spied of his own clan. He assured the third Hokage and Danzo that there definitely was going to be a coup d'etat against Konaha. The third Hokage wanted to solve this through peaceful negotiations; however, Danzo sent the order to Itachi to slaughter his own clan and become a rogue ninja to save Konaha from war. Though this decision was very radical, it saved Konaha.

Although Itachi takes 70% of the credit (with Obito having 20%) since he is the one who fulfilled this daunting task, Danzo came up with the idea and gave the order to him to save Konaha.

•He tried to steal Kakashi's eye.

While Kakashi was in Honaka's Anbu Black Ops, Danzo wanted a new sharingan. Kakashi, who received his sharingan from Obito, was the only one known to have the sharingan at the time so he used Yamato to try and steal his eye.

Wtf Danzo! How could you try to take the eye of someone so amazing!?! You'd have to be one sick motherfuck to do that to Kakashi!

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•He stole Shisui Uchiha's eye.

Shisui Uchiha was Itachi's best friend and planned to stop the Uchiha's revolt by using Kotoamatsukami, a genjutsu that alters one's mind to how the user sees fit (kinda like the mind control thingy in Star Wars except it is a dōjustu, meaning that it is used by one's eye) on the Uchiha clan's leader, Fugaku Uchiha, Itachi and Sasuke's father. However, Danzo wanted Shisui's eye for himself because he wanted to protect Konaha in his own different way.

•He killed Kōsuke.

Whenever Pain attacked Konaha, Kōsuke was sent by Tsunade to get Naruto back to Konaha. Danzo saw this as a stupid decision since the Kyūbi inside Naruto was what Pain was looking for and killed the messenger toad. However, preventing Naruto from fighting Pain was a very stupid decision since Naruto defeated Pain and saved Konaha.

•He wanted the young and innocent Sasuke Uchiha dead.

Even though Sasuke was but a child ignorant of the whole Uchiha coup d'état, he still wanted Sasuke dead. It is debatable that killing pretty much all of the Uchiha was a good thing to keep peace in Konaha; however, killing a child that has no idea what is going on is very harsh. Itachi, the most badass character ever, made sure that Danzo wouldn't fuck with Sasuke by threatening to tell secrets of Konaha to other villages.

•His intention is to protect Konaha through any means necessary.

Although many of Danzo's deeds seem harsh, his main endeavor is to protect Konaha. He does not wish for fame and recognition, he accomplishes his wishes through the shadows.

During the Five Kage Summit, Danzo used Shisui's Kotoamatsukami to trick the five Kages into working together to stop what was believed to be Madara Uchiha at the time. However Ao of Kirigakure (The Hidden Mist Village) saw this trick with his stolen Byakugan and called Danzo out on his deception.

Now let's talk about how Danzo fights.

During the Danzo vs Sasuke fight, Danzo had some pretty cool tricks up his sleeve...literally! Look at this shit!

Danzo uses the Sharigans on his right arm to use Izanagi, which turns what you perceive as reality into an illusion. Whenever he was hit by a fatal strike, he would use Izanagi to revoke the attack. Every justu has it's weakness though. Danzo lost one of the Sharingans on his arm every 60 seconds that Izanagi was active.

Donzo uses a big elephant thingy called Baku as a personal summon. Baku uses wind to suck like a vacuum. Baku tried to suck in Sasuke but he used this as an advantage and used his fireball technique against Baku.

Danzo was cabale of using Hashirama's, the first Hokage's wood element because Orochimaru gave Danzo Hashirama's cells.

Whenever Danzo was defeated by Sasuke's Chidori Eisō, he used his final moments to try and seal Tobi and Sasuke in his corpse with Ura Shishō Fūin.

So vote whether you hate Danzo and think that he is a horrible person, dislike like him because of his decisions but still like that he is just trying to protect Konaha, like him because you think his actions (although harsh) are sometimes necessary for peace, or....if you love him. Personally I can understand liking Danzo but loving him is just too much. He's done too many bad things in my opinion; however if you do love him, tell me your reasons. Make sure to comment on what you think about Danzō.

(Thanks to http://naruto.wikia.com/wiki/Danz%C5%8D_Shimura for proving information on Danzo.)