"A source is not credible if it has no fact to back its claims."
Absolutely wrong. A source is credible if it has a proven record of accuracy, regardless of what "facts" it may have in any given case.
I put "facts" in quotation marks because there are always those who will deny or assert anything as "fact."
"Did this "nurse" sign a criminal complaint? What is the name of the hospital? Name of the doctor in charge when this murder occured? Police report? Any verifible facts at all?"
You don't know much about life, do you?
"I don't know if Alan Keyes is a liar. He may be just a gullible fool."
Extreme skepticism is just the mirror image of gullibility. Both are folly.