Well first off you have to go by the percentage of error here. You know, since you actually have studied polling before, that the 3% margin of error is there for a reason, as, mathematically that's the spread of variation that can come in a group of 1000 with answers as direct as this. Simply put, 1000 people polled in this manner is generally far more reliable than anything that the white house puts out for polling, more reliable than news organizations and nearly as reliable as something Zogby would do. So while it's fair to say that this wasn't polled across a proper locale, which is fine, then we'd have to call into question every single poll ever done with any variation of 3% or higher.
To your second point, there's a difference between living, breathing rights enumerated in the first amendment and knowing the first five presidents (washington, madison, jefferson, adams, jackson... i believe... adams could be wrong. he might have been sixth) from a historical perspective. Knowing your rights is something that is applicable every day to every person living in this country, whether it's eating your cereal and knowing the laws that went into what you eat or being able to travel the roads freely on your way to work. The importance of knowing your rights like this are so astronomically more important to american lifestyle than history that I really can't believe you'd compare these two topics.