Do people undestand that if you say a liberal said this and then point to a right-wing blog, that is not proof it was said?

Citing quotedb.com doesn’t cut it either. They have countless UNCITED quotes. For a quote to be reliable it needs to have a time and an occassion. You must be able to find the quote from a reliable source (like the Library of Congress or well established memorial organization) along with the speech or essay it came with.
I’ll give you an example:

“You can’t say you love your country and hate your government.”
- Clinton supposedly after the Oklahoma bombing.

I tried looking up this quote everywhere along with the speech it came with. So far nothing but right-wing blogs and political websites or amateur quoted websites without the actual source.