"What they left out in the Fri. "thumbnail" were all the comments about "...middling interest", "...comparison to the hilarious spoof to A Mighty Wind".   The former was negative, the latter a subjective comment written as a fact.   "

Maybe I'm alone in thinking this, but I don't take "middling interest" to be such a negative comment. She said "Younger generations whose introduction to folk music came via Mr. Guest may deem the film of only middling interest."   That is very true. This is not a film that will appeal to a young people in large numbers. Of course there will be some interest from enlightened young people, but this is not a film that will make their "must see" lists.

Also, she NEVER compared it to A Might Wind. Read it again, she said "If the premise sounds familiar, it's because Christopher Guest's hilarious spoof ''A Mighty Wind'' (2003) was modeled after Leventhal and his devoted collaborators. And although a documentary involving people and events that have already been satirized could easily be a target for further ridicule, Jim Brown has managed to beat the odds."

THOSE sentences are congratulating Brown for avoiding the obvious comparisons to A Mighty Wind.   Her comments are legitimate, not negative. You may disagree that "A Mighty Wind" was a "hilarous spoof", but that is far from the point. She gave her opinion of A Mighty Wind, not stating a "fact".   

There was no "slanted editing" in their capsule review.