The former, I believe (assume you mean TSA later in 2001, not 2011). I'm talking about this in the context of answering Boggie Dog's question. There are two rationales for screening aviation passengers:

1. Safety of other passengers. In this case, a smaller plane means that someone who intends harm has a limited number of people he can hurt. Pax are free to make the decision that they don't want to fly on a plane where pax don't go through security inspection.
2. Safety of the non-flying public. The non-flying public have a safety interest in ensuring that planes aren't turned into weapons. Hence, the general public has grounds to require a reasonable level of security on board aircraft. In this case, a plane with lower speed, size, and range represents less of a danger to the non-flying public, reducing the rationale for spending a given amount of money to secure that plane.

Note that I believe that both interests 1 and 2 can be fully satisfied for all types of commercial aviation through, at most, 9/10/01 levels of security (metal detector and baggage x-ray), particularly with reinforced cockpit doors on aircraft.