That's true-- although just based on my observations it feels like Facebook comments on popular posts are silly because of how angry/polarized they are, not necessarily how nonsensical they are (relative to Youtube's comments historically).
For example: typical bad Facebook comment = angry rant at Sean Parker from person who seems genuinely angry
vs
typical bad Youtube comment = some nonsense troll/needlessly racist comment.
Perhaps, although I've seen an awful lot of trollish/bigoted Facebook public comments on anything related to politics — it's not as bad as YouTube but increasingly close.
For example: typical bad Facebook comment = angry rant at Sean Parker from person who seems genuinely angry
vs
typical bad Youtube comment = some nonsense troll/needlessly racist comment.