From my personal interactions, and with my personal perspective of how Facebook has publicly conducted itself over the years, having worked at Facebook would immediately raise red flags in my mind about the philosophical perspective of the potential employee for having worked 'at will' at the company. Context certainly matters, but it would be become a point of conversation. Not all that different from a health-professional being wary of hiring someone who used to work for a tobacco company.

To me it would indicate the possibility that the person might not want to understand the wider implications of their work, might understand those implications but not care about them so long as they are personally or socially enriched, or might just agree with the duplicitous nature of the company. There are of course circumstances to account for, and everyone's reasons are different - but the above rationalizations would raise red flags for me - especially in my industry where thinking about wider implications of our work is absolutely critical.

I am not the GP but I totally agree and the same goes for NSA employees. They have proven they are okay with violating the privacy rights of a billion people.