Correct. I have no skepticism that Mueller is
claiming to have such evidence
.
That's not what McCarthyism was, but fortunately we don't have to jump to conclusions about what evidence the federal intelligence agencies does or does not have. The judge was given information under court seal. You are claiming that Mueller was making an "McCarthyist" "excuse" in the explicit absence of evidence.
The investigation and court cases are going to proceed, so jumping on not having access to information that is specifically not publicly available to somehow argue that such information doesn't exist is a ridiculously short-sighted and nonsensical strategy.
Except for Trump's team and Republican propagandists, where undermining Mueller in the court of public opinion while he is investigating in necessary silence allows for a few outs. The first that the Special Counsel's conclusion can be weathered by the Republicans in Congress if it can be sufficiently discounted as partisan, witch-hunt, etc. The second that interfering (via firings or other means) can be excused for those reasons.
). Isolate an incident as if it never happens outside of this one time, then be like, "What the? How come I do this one thing and all of a sudden I'm a Trump supporter?!?!?" 
