I agree with this to a certain extent, but one holds something in suspicion with the goal of testing it, checking out the claims to ascertain the overall worth. Are we doing that? Critical thinking is a good thing, but if we don't follow through, then we're doing the very opposite of critical thinking: we'd be suspecting something for the sake of suspecting it, without giving it due thought.

Your charge really is that the author might be sloppy and careless. One point doesn't show that. It may just be an innocent mistake, especially if it has no impact on his larger argument. It would be of benefit to those of us reading this if someone could point out examples of carelessness that matter crucially.