Unfortunately, Benjy wasn't someone who was very good at reading people or their minds, and when Alastair pulled away from him, he only took it as confirmation that he didn't really want help. And he didn't really know what to do with that. Well, he didn't know what to do with him not wanting any help while also not wanting to be left alone.
Finally, he asked, "What do you need?" in the hopes that that, finally, would give him the slightest clue what to do here.