...is out, people. The biggest argument that I still see against Gnosticism is that it was secretive. The implication, without fail, is that this was a dirty secret. It was so secretive in fact some of the various Gnostic groups were known about in their own time, so secretive that there are tomes written by the likes of Irenaeus against them. It's needless to say that it wasn't a very well-kept secret.
What about now? The links to the many gnostic blogs on this page? Those aren't secret. The Nag Hammadi Library collection over at gnosis.org? That's not secret either. In fact, if you're willing to learn about Gnosticism, however broad a category that is, you'll find information plastered ALL OVER the internet. Information is also published in books at your local library or bookstore, and in academic works that may be a touch out of reach for many people, both because of their cost and academic jargon, but nevertheless, they are there. They are not secret.
So what is the real secret? It's not that you can't find the information. The real secret (which also isn't really a secret) is that you probably won't understand the information when you find it. That doesn't make you stupid, and those of us who do think we understand it, in any extent, don't think you're stupid. (We really don't think we're better than you. I'm sorry to burst that bubble.) The truth is, most of us don't fully understand it either and you would be hard-pressed to find a "modern Gnostic" or academic who will claim to. If they do they're probably lying. In fact, the real, REAL SECRET, is in the journey, and the journey only takes on meaning if you're walking it, however that may be. Anyone can walk it. Whether it's a journey that is right for you is for your own determination. Gnosticism is not something everyone will embrace, and it never will be.
Gnosticism is a complex issue, both from the perspective of those who practice it in a contemporary religious form, and for those who spend their lives studying classical Gnosticism and its umbrella of related topics. To make a practice of reducing it to such simplistic buzzwords, "secretive, elitist, dualistic", etc., is at best ill-informed, and at worst disingenuous.
By the way, if you look at all of the links on this page, click on them and see that there is indeed a vibrant modern Gnostic current, you'll see that those arguments aren't really working. "I'm just saying...", as they say.