In the eyes of `Ali...
In the eyes of `Ali, such an action was in fact a kind of expropriation from the baytu 'l-mal (the Treasury of the Muslims) without giving notification to, and obtaining permission from, the leader of the Muslims. For this reason `Ali gave the order that they should take off the garments and put them in a particular place, until they could be delivered to the Prophet and he himself could make a decision about them.
Because of this, `Ali's soldiers became disgruntled, and, as soon as they had gone in to see the Prophet, they complained about `Ali's harshness over the garments. The Prophet addressed them, and said: Oh men, do not grumble about 'Ali. I swear by Allah that he is more intensely in the way of God than that anyone should complain about him. (Ibn Ishaq, The Life of Muhammad (transl., A. Guillaume) p. 650.) Ali had no concern for anyone in the way of God.
Rather, if he showed interest in someone or was concerned about him, it was because of God. Naturally, such an attitude makes enemies, and it causes offence to souls full of greed and craving and brings them pain. None of the companions of the Prophet had devoted friends like 'Ali did, just as no-one had such bold and dangerous enemies as he did. He was someone who, even after his death, had his corpse attacked by enemies.
He was himself aware of this and foresaw these things, and so he left as his will that his grave should be hidden and unknown to all but his sons, until after about a century had passed and the Umayyids had been overthrown, the Khawarij overthrown too, or made all but impotent, and vendettas and avengers had become few, and Imam as-Sadiq indicated the sacred soil of his resting place.
In the period of his caliphate, `Ali expelled three groups from beside him and rose up to do battle with them: the people of (the battle of) Jamal, whom he himself named the Nakithun (those who break their allegiance); the people of (the battle of) Siffin, whom he called Qasitun (those who deviate); and the people of (the battle of) Nahrawan, the Khawarij, whom he called the Mariqun (those who miss the truth of the religion).
[^1] `Ali said: When I took up the reins of government one party broke their allegiance (nakathah), another missed the truth of the religion (maraqah), and another deviated (qasatah). [^2] The Nakithun were of a money-worshipping mentality, people of covetousness and displayers of prejudice. `Ali's speeches about justice and equality were more for the attention of this group.