They're helping. The way they're helping might be stupidly longterm, the salvation they offer may be unwanted, but they're helping. That's what Naaru do. That's the way of the Light. Misguided altruism can be as dangerous as malice, especially when you feel you know better about what others need. As eternal and incredibly wise beings like the Naaru, gifted with prophecy, doubtlessly feel is true.
And likewise, this doesn't mean Locus-Walker is a villain. What it does mean is that he's Void. His characterization is similar to Xal'atath. Cold, curious, irreverent, amiable, and utterly untrustworthy. He's probably not even an Ethereal. But as Blizzard said, the Void is more grey.
Locus-Walker, like the Void, is driven by self-interest. He's not altruistic in the slightest. He helps others when it helps himself, but his self-interest is more enlightened than most. He understands not to present himself as a direct antagonist, and instead to guide people more subtly in pursuit of his goals and knowledge.
As a Void being, he can never be trusted implicitly. He'll always act for himself. But that doesn't mean he's a villain. Just as the Naaru's desire to help doesn't make them heroes.
Locus-Walker represents the Good of the Void. He's clever, ambitious, independent, and curious. A sly roguish sort who understands the value of playing nice and not being stupid. The latest Naaru we've seen represent the Evils of the Light, believing they know better about what we need and so coming up with "Higher being" plans to help us.