I disagree with your analogy. It's akin to saying not a single observation is ever valid. Lots of observations are accepted as evidence in science. The people you are trying to compare me to didn't just make an observation, many of them drew an unsupportable conclusion about what they were observing. People make repeating observations in some areas, (ghosts, bigfoot, UFOs, homeopathy and so on) and with those specific observations we've looked and repeatedly failed to find supporting evidence. In addition a lot of evidence cannot be found where we should expect to find that evidence
There is a thing called lack of or the existence of corroborating evidence. There are trained observers and observations that are more reliable than others. There are observations which are less reliable such as an eyewitness to a crime committed by strangers. But if that same eyewitness sees their close friend commit a crime, that observation is more reliable.
You make a foolish mistake if you treat all observations equally.