That's kinda the point chum. Libs won't attack a source that is liberal.
That's the MO of those sealions - ask for a source. When a source is provided, attack the source. Example "OMG I can't believe that you think I'd believe anything from FOX News (or insert any other source here)."
That's the game, no source is ever good enough, like we're submitting our doctorial thesis or in a court of law here, not making memes for lulz.