Evidences?
Lack of evidence to the contrary. When people disagree with something, they generally say so quite loudly. When people agree with something, they are usually much quieter. I've seem plenty of people complaining about the application of BLP to a particular article, but few complaining about BLP in general.
If we go by what happens BLP does not exist unless an admin with an agenda turns up.
*shrugs* Then that's the policy.