It's easy to take nothing from the thoughts of another when you yourself have nothing to give.

My personal observation is that there is a lot of close, personal interaction at top tier schools. So, while this isn't entirely wrong, its missing a useful observation. Academics working in a curated environment encounter the best ideas and encounter less 'noise' from bad ideas. This isn't a problem that's easy to solve, although technology is slowly chipping away at it. Currently there's not substitute though, for being in the same room with Picketty and other smart people, which probably happened when Picketty visited MIT after the publication of Capital in the 20th Century.

Generally speaking, ad-hominem is best served as a side-dish. Or not at all.