He knew before he went in. Lawyers who do trial and appellate work before judges are accustomed to more rigor and QA on evidence, but even there plenty of lies and twisting of law are normal - that what "adversary system" is about, both sides twisting truth, hoping to convince the rubes in the jury that their version of reality and law is the correct one.
Likely he's not had a client who was railroaded by a corrupt DA, which is the analogy that fits the House DEMs. Abuse of power and process for political gain.
At any rate, those sorts of abuses tend to get one hackles up unless you don't like the person being abused. I'd pile on if the target was somebody in the press or any DEM. Lock 'em up for chewing gum, for all I care.
I had seen an earlier interview where he said he was personally “attacked”, his law firm was under siege and his home vandalized. I have the impression that he had never been in quite that kind of situation before.