That people I respect who used to be free speech advocates now are talking about "low value" speech etc. Check out the quote from Daniel Solove: “the law is hampered because it overprotects free speech.”
Different levels of speech get different protection (political speech, commercial speech, etc.) but I don't like the term "low-value speech". Who decides the value?
Defamatory speech isn't protected. But I still don't think "low-value" is a helpful description.
For example take comments on Slashdot or wherever saying "first post" (or "first comment" or whatever). Do they have value? Most would say no. Does that mean they shouldn't be protected?
Defamatory speech is also protected to a degree because it isn't possible to weed out beforehand, but carries consequences and could be censored after the fact.