I disagree. Bill James looked for evidence that catchers have measurable impact on pitchers' ERA, and he looked for many years. He found none. However, absence of evidence is not evidence to the contrary. It very well may be that there is a cause-effect relationship in isolated cases that is swamped by noise when averaged over all catchers, hence unmeasurable. Which means it's essentially an opinon issue. Therefore those that don't believe if that relationship being meaningful are not "kidding themselves".