To justify his actions, one would have to see that Odysseus was acting as a captain, a leader of men. Odysseus recognizes that the fulfillment of the mission was the most important reality guiding his actions. Accordingly, if he were to tell his men about what dangers Scylla posed, he recognized that it would cause unnecessary panic. The result of this would be a detracting from the mission at hand. He understands that telling his men and carrying out the mission are compelling motivations. However, in his role as a leader, the latter wins out. For Odysseus, this becomes his intent. It is the same type of intent seen in a general who knows that a specific amount of soldiers will be lost in undertaking a specific battle. Like the general, Odysseus understands his actions and does not run away from the implications of his actions, even in retrospect:
We in fear of destruction kept our eyes on Charybdis,
but meanwhile Skylla out of the hollow vessel snatched six
of my companions, the best of them for strength and hands’ work,
and when I turned to look at the ship, with my other companions,
I saw their feet and hands from below, already lifted
high above me, and they cried out to me and called me by name, the last time they ever did it, in heart’s sorrow.
"Heart's sorrow" is a way in which one can see that Odysseus feels agonizingly bad over the loss of his men. He did not sacrifice them in a trivial manner.
In optimistically viewing Odysseus, one sees the loss of his men as a necessary evil that he acknowledges. However, if one were to make the case against his actions, I think that one of the primary rationale would be based on metrics. If Odysseus valued truth and honesty to men who have pledged their lives and honor to him, he would have felt compelled to tell them about what lay ahead. In this case, consequences such as the mission are secondary to honoring a commitment to one's duty towards honesty. At the same time, Odysseus is crafty enough to recognize that his "sorrow" is the public declaration of what he must feel. In retelling the tale to the Phaeaceans, Odysseus understands what he has to do in order to make his own decision look acceptable. He is adroit enough to "spin" the tale so that he could appear socially respectable for his actions. If one were viewing him in a skeptical light, it would become clear that when he arms himself for battle, he understands that he, himself, did not want to be taken as one of the six, so he had little equivocation is delineating his own importance over that of his men. Like so much with Odysseus, complexity reigns supreme.
In the final analysis, when examining his actions of not telling his men about Scylla, Odysseus's actions have to be reduced to what perceives as his primary motivation. If one sees that his motivation was acting as a general and leader of men, then his decision to withhold critical information can be seen in one particular light. If one sees his actions as more self- serving, then his actions are seen in a more skeptical and critical frame of reference.
It would be wrong not to tell your crew where you would be going, since it should be their decision whether to go or not. However, he didn't tell them because he thought they would be scared and panic. He was the captain and made the decision to go on. That doesn't really make up for the fact he was putting their lives in danger. I see his actions as wrong and he shouldn't have kept secrets from the crew members.