What they are really looking for with the basic security clearance is a somewhat boring individual who fits in with the system and feels that the system is pretty darn good. If you do not file taxes because you are impoverished, that may not be you. If you think your doctors are only concerned about themselves and money and that the medical system is fundamentally screwed up, that may not be you. If you think that the poor are treated badly in this country and that the legal system and government is designed to exalt the rich and disenfranchise the poor, and that there is gross state-enforced inequality of opportunity, that may not be you.
Besides with the disaster that is or was Ed Snowden, I would think that the whole security clearance system would be up for reconsideration and that they would be much better off with people like me. Just my opinion.