I do agree with what you're saying overall, but I also think that some of these so-called non-football people are more intelligent and watch more film than many teams do.
There are many situations in which they are wrong, but there are also situations in which teams are drafting for need, and other teams simply just don't like a guy, so he falls. I think Matt Leinart is a perfect example of this, falling all the way to #10 from what would have been the first overall pick last year.
So while I think you make some valid arguments, I don't think its applicable all of the time.
Also, one part of being a fan is rooting for your team to make good decisions, and then living or dying by them. We like to have some way to judge a team's draft, as its fun to do so, and as crappy a system as we have relying on the "experts", its the best one we've got.