That may be true, but is not what I would call user friendly, you have to seek out something you may not know exists. I.M.H.O. if you are going to flat out remove sources, you might as well remove the data the source represents. Is anyone suggesting that? I certainly hope not. So yes, I.M.H.O., the first rule should be do no harm, do not remove less than perfect sources (which often can point you in the right direction) unless you replace it with a better source.
Under the current standard, things taken as personal knowledge 100 years from now could be wiped out as a source, without a primary document. Genealogies published 100 years ago were filled with personal knowledge, collections of far flung individuals pieced together. Should all those be tossed out?
I understand the desire for "purity" in wanting to purge things less than perfect. However, we should not let perfection be the enemy of progress, when that less than perfect source can point someone else in the right direction.
Bad Idea