Just read an email where my application for the Online Film Critic's Society was rejected, on the basis that my reviews are not up to their level of quality, I don't offer meaningful and distinctive contributions to film criticism, and that my website is not professional looking. I didn't expect to make it in, but it still sucks.
Being rejected is never nice. How shallow it sounds I hope you'll not let the disappointment overwhelm you. As far as I understand from their website you could always apply again next year. If this really is that important to you - make it a project to come up to their standards. Look at their current member's websites. How are they different to yours? Is there any way you could change in that direction to become more like them?
On the other hand you might ask yourself: do you really need to be a member of that society? I figure yes if you're aiming for making a living out of writing about movies, but if it's just a great hobby, why not let it be that way?
If you ask me I think personal blogs are more fun to read than the websites of the members of that society. I didn't recognize any of them, but I checked out a handful and I thought to myself that it wasn't for me. Not personal enough.
However, if you really, really are aiming for that, you shouldn't be put off by that letter. It's not the end. It's just a start on your way into the club.