Yup, he's correct. Everyone has a viewpoint which can in theory bias them one way or another especially when politics is involved. Which doesn't mean they can't set it aside and do their jobs. The problem with most conservatives is that their own partisan bias is so strong they just project it onto others, and assume no democrat would ever do his job properly when politics is involved.
And also, an investigator isn't a juror. Juries are the arbiters of guilt or incident. If a case built by investigators is a bad one, we have a jury and a judge to later act as gate keepers.
Watched part of it this morning before leaving for work. Strzok is no dummy.
As I've said from the beginning the idea that investigators would have no opinions about those they are investigating is ludicrous. Is the expectation that FBI investigators don't think one way or the other about a murderous mob boss they are going after? That in The Silence of the Lambs Starling was supposed to feel indifferent as to Buffalo Bill? I would imagine disliking the people they investigate is the rule rather than the exception as...well...investigating unsavory people is kind of the job.