Recently, the notorious and squid-loving PZ Myers "desecrated" a communion wafer. Something about the objections to PZ's conduct strikes me as odd, though, so allow me to ramble through some reflections on desecration and the respect we do (and don't) owe religious beliefs.
It's not possible to desecrate anything but the holy. That's what the concept of desecration is all about, after all. You can't desecrate wafers unless they're holy. But what do we mean by "holy"? We could mean really holy, as in actually blessed or otherwise sanctified by a supernatural being. But I defy anyone to prove that such a being exists. Instead, I take holiness to only exist within a practice of taking things to be holy. (To be fair, I am tempted to say the same thing about most things: moral good, for example, only exists within a practice of taking things as morally good.) Given that, since PZ is not in the relevant practice, it follows trivially that he is not capable of desecrating the wafer.
Now, one option at this point is to claim that the practice itself holds that everyone, regardless of choice, is part of the practice. That is, the practice claims, by its nature, to be universal and objective. (Practices about knowledge fall into this category; we have knowledge-generating and -accepting practices, but these practices include a claim that what is discovered is objective and actually true.) But this doesn't work for religious practices. Because a mark of a religious person is the acceptance of the practice -- the willing acceptance. (Sometimes, this is called "faith".) One who has no faith may be wrong -- a moral point -- but this person clearly is not part of the religious practice. So, religious practices do not include a claim to objectivity; thus, religious practices do not create holiness for everyone. Hence, those who do not accept religious practices cannot be capable of desecration.
So, those who are offended by actions like PZ's on the basis of their own religious faith are, oddly enough, being faithless themselves (we could consider this blasphemy or simply impiety), because inherent to the religion they practice is the notion of freely accepting the practice. To try to compel PZ to be a member against his will is thus intrinsically impious.
However, there are also those who argue that PZ's actions (along with his generally intemperate attitude towards the religious) are somehow damaging to atheism. That is, these atheists hold out hope that, without those like PZ (so, Richard Dawkins, Daniel Dennett, and so on), it will be possible to "convert" the religious. I tend to think that this underestimates the problem of sunk costs, i.e., the tendency of people to incur greater costs for something that has already cost them a significant amount. Or, that people don't like to walk away from an investment, and will tend to hang on to it long past the point at which it becomes irrational (in either the economic sense or a broader one). The religious aren't going to convert any time soon, because they've invested too much -- too much time, too much care, too much attention -- in their religious identity. (And that's ignoring the whole issue of "identity" that's under the surface here.) So, removing PZ from the equation wouldn't accomplish anything useful.
But, do religious practices deserve respect? Not all practices do, clearly. Lynching and apartheid were widespread practices that morally ought to be condemned. So, I tend to think that respect for persons -- equal concern and respect, that is -- comes first, and practices must fit within it. (Which, I suppose, is an assumption that ethical practices are the most fundamental practices we have; anything that conflicts with them must give way.) Lynching and apartheid are wrong because, even when widely accepted, they conflicted with basic ethical practices and norms. Similarly, a religious practice which conflicts with ethical practice -- say, one involving human sacrifice, or one requiring the deeply impoverished to bear children they cannot afford to raise -- is a religious practice that does not deserve to be respected. So, PZ's mockery of religious practice may actually be ethically justified -- possibly even required.
Is there some feeling of the sacred that is worthy of respect, apart from the religious practices themselves? Perhaps. I'm not immune to it, for all my cynicism, skepticism and general misanthropy. Pagan symbols tend to do it for me, such as the suncross and Celtic cross. But here we must say, surely, to each his own: because what we're referring to is nothing more than an aesthetic experience, a preference grounding out in taste rather than basic practice or fundamental nature. That is, as soon as we start talking about a feeling of the sacred, we lose our grip on faith (assumed by religious practice) and holiness (defined by religious practice) and come up with something relatively squishy and nebulous. Something like an aesthetic experience that one finds fulfilling and pleasing. Which is fine and dandy, but how, exactly, is PZ Myers obligated to ensure that anyone has these feelings? (Indeed, is anyone obligated to ensure that PZ Myers has these feelings?) Surely aesthetic experience is a personal problem, to be solved by individuals on their own.