Earlier quoted context omitted.
According to the epistemological principle of not being proved wrong while containing a reasonable amount of evidence to indicate that their report is in all probability true. Why are you asking such a vague, open-ended question?
A great deal of what Snopes does (particularly in recent years) is much closer to "opinion" than "fact", especially when they start labeling things "mostly false" or "mostly true" or whatever. You can't do that when you're dealing with actual facts.
"The sky is blue because other stars reflect blue light onto our atmosphere." How would you rate that, given Snopes' scales?
Do you have any specific examples where there was a concise yet opinionated decision on any published articles from Snopes that don't rely on hard evidence for their conclusion?