I think that a good case can be made that Odysseus was justified in taking action against the suitors. Part of any justification of Odysseus's behavior resides in the dishonorable way that the suitors treat his home and its inhabitants. Homer shows honor as a critical aspect of Greek society. It is the reason why the war against Troy is fought. Honor is vitally important to the Homeric Classical setting. It becomes evident that the suitors bring a sense of dishonor to Odysseus's home. The fact that they overtake the residence without any regard for the man of the house itself is one example of dishonor. Additionally, the suitors vie for Penelope's hand in name only. The suitors are there for the prizes of Odysseus's home and show little in way of respect for the traditions and sense of decorum that Penelope displays. Penelope herself says as much in challenging the suitors to string Odysseus' bow:
Listen to me you suitors, who persist in abusing the hospitality of this house because its owner has been long absent, and without other pretext than that you want to marry me; this, then, being the prize that you are contending for, I will bring out the mighty bow of Odysseus... and quit this house of my lawful husband, so goodly, and so abounding in wealth.
Penelope's statement indicates behaviors that would justify Odysseus's anger. The persistence in "abusing the hospitality of this house" as well as the "pretext" of marriage can be combined with the "abounding in wealth" as independent reasons why Odysseus' anger is justified. In the larger sense, his anger is further substantiated by hearing his wife speak these words. There is a despondency present in Homer's depiction: Odysseus having to see his house reduced to an undignified state and seeing his beloved wife imploring the men who disrespect his home to simply listen to her. This instant could be seen as a justification of his brutality towards the suitors.
A potential argument against Odysseus's actions suggests that he must assume a more magnanimous stance that would reflect his position as a king. Odysseus should act "more regal" and refrain from violence. This argument would also suggest that he should not sink to the level of the suitors. Yet, it should be noted that Odysseus does not instantly slaughter the suitors. He approaches them, in kind and disguise, with a sense of dignity and aplomb. He even suggests a "way out" for the suitors:
Suitors of the illustrious queen, listen that I may speak even as I am minded. I appeal more especially to Eurymachus, and to Antinous who has just spoken with so much reason. Cease shooting for the present and leave the matter to the gods, but in the morning let heaven give victory to whom it will.
Odysseus accepts the abuse from the other suitors while he is in disguise. He does not retaliate. Yet, it becomes clear that the suitors only wish to usurp Odysseus, living off of his endeavors and the fruits of his labor. This is the highest amount of disrespect and dishonor. Once it becomes clear that there is no "philos" (Greek for love and respect) towards Odysseus, and little in way of loyalty, he strikes. Odysseus could not have re- asserted control in any other manner. He had to take action against the suitors, something that in the name of honor and loyalty he saw as completely justified.