1) “90% of everything is crud.”*
2) “Nothing is absolutely so.”Theodore Sturgeon
Law number one is most useful for rebutting (or ignoring) attacks on a a genre of art, field of study that cite its worst quality items as examples.
Number two is helpfully applied to aphorisms of (almost*) all kinds.
More context here.
*Sturgeon called this first statement his “revelation” and the second his “law”, but the first is the one people talk about.
**almost: “Everything in moderation… including moderation.