Consider the source-- a PSA

This post's title (the first part, anyway) is something my mother often said to me when I was a kid and I complained to her about someone insulting me. The meaning: Think about who said this. Are they really credible? Is it worth taking what they say seriously? If not, shrug it off. It's not worth your time. Only take seriously the criticisms of someone equipped to criticize.

That's good advice. You know what else is good advice, though, paradoxically? To consider the words while disregarding the source:

“The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread.” 

"When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours."

These are good quotes, regardless of who said them. There are certainly many different occasions on which it's important to note the origin of a quote-- if it's the insight of someone who discovered something, the emotional outlook of someone who experienced something extraordinary, a moral judgment from someone who was revealed to have done precisely the thing described (i.e. a hypocrite), an incidence of intentional or unintentional irony, and so on.

But if the quote is simply profound, witty, insightful, worth repeating for its own sake? Do so-- absolutely do so! But cite the author in order to do credit to him/her, rather than to use that person as an authority whose gravitas or expertise is supposed to automatically render the statement true or meaningful.  And never just assume that whomever is attributed as a source necessarily is. Especially on Facebook.