Perhaps a better way to put it is: Sasquatch evidence is like bubbles...easily popped.
One can build a house made of bricks of good circumstantial evidence but since almost nothing in sasquatch "evidence" meets the criterion of good circumstantial evidence one has nothing substantial at all.
Good circumstantial evidence requires a FACT to be presented that when considered by itself or with other evidence (circumstantial or direct) points to a likely conclusion. For example a fingerprint proven to be that of the defendent at the scene is good circumstantial evidence that the defendent was at the scence at some time. A fingerprint that may or may not belong to the defendent that is found at the scene is NOT circumstantial evidence that puts the defendent at the scene because a proven FACT is not available to ascertain anything about where the defendent was.
Since it is impossible to ascertain whether any footprints, hair, smell, sounds, tree-breaks, stick formations, rock piles, are, in fact and without a doubt, from a unrecognized by science legendary creature called sasquatch or Bigfoot; it is then erroneous to offer any of it as good circumstantial evidence.