It reads to me not so much as an ad hominem as an explanation of why he sounds so bitter towards academia. "He's only had one second author pub" is, almost uneq

It reads to me not so much as an ad hominem as an explanation of why he sounds so bitter towards academia. "He's only had one second author pub" is, almost unequivocally, a statement that he hasn't been academically successful. Maybe it's because he's not good at science, maybe he's not good at gaming the system around science, but something is off. Without hearing him talk about his work in something like a seminar (and being fairly familiar with his specialty, which I am not), it's really hard to say. I won't argue that the publishing system is perfect, but in my experience, it's really not "corrupted" in any meaningful sense of the word, and that good work will find a venue (even if not a glam journal). I think really the point that the GP is raising is that, protestations to the contrary aside, the OP really is bitter. Maybe they are truly disillusioned by the system around science, but such a critique does hold more weight coming from someone who has done well.