OK, I'm not a meta, so please feel free to take my advice with a large grain of salt.
The description was just one place you should have looked. Another thing you can do is look at similar categories -- e.g. the "parent" category (one level up), "sibling categories" (in the same level), @-linked categories, sub-categories (if any), and related ("see also") categories. These can help you decide if a site fits best in your category, or would fit better somewhere else. Although adding sites to a category is a big part of being an editor, another part is knowing when sites would be better found elsewhere.
Another place to get information is to search the ODP (or the Google directory) to see if the URLs you are proposing are listed elsewhere -- and more importantly, if they are, to try to understand why. In this case, if you had searched, you might have found that iprepare.com was listed in the category above the one to which you were applying, because it doesn't just offer security supplies. We try to avoid having a site listed in both a parent and child category in the same branch. I'd like to emphasize that (as far as I know -- I'm not a meta, remember), there's nothing wrong with submitting sites that are already listed elsewhere, as long as they would be appropriate in the category for which you are applying.
Finally, it's somewhat dangerous to assume that all the listings in a category are correct. Mistakes do happen (we are only human, after all), and listings can be overlooked when the directory changes, for example. If you use the majority of sites in a category as a guide, look for category descriptions, look at similar categories, and check out your URL's first, you would be much safer. I think you would probably admit that the two sites you mentioned having submitted weren't exactly in the mainstream of that category.
I suppose you could appeal to staff, but honestly, I doubt it would get you anywhere. As far as I can tell, the ODP isn't exactly a legalistic, litigious organization. When editors receive constructive criticism (and most of us do at some point), we are expected to try to improve, rather than to look for avenues of appeal (although disagreement through constructive discussion is both expected and encouraged as a process to help the directory mature). If we didn't take the advice of the editing community, and work as a team, the directory wouldn't work nearly as well as it currently does.
I also hope you'll take note of some reasons why I think you should feel encouraged, rather than "rejected". Shopping/ branch categories are notoriously tough for first-time editors to get (due to large amounts of spam and attempted abuse). Also, you probably wouldn't have received any personal feedback if the reviewing meta didn't think your application was worthwhile, at least in part. If I were you, I would try applying again, either to the same category (this time selecting the sites more carefully) -- or perhaps to a Regional/ category (perhaps your hometown, or a subcategory if it is a large town), just because there are a lot of good small regional categories that could use some development, and aren't spam magnets.