Not long after I published the original essay with a title something like this one, Steve Savage chimed in and said, half-kidding, "Don't worry about someone stealing your good ideas. Worry about someone stealing your bad ones!" I think he is in fact right.
This goes back into something else I've touched on from time to time — the way massively successful or influential things have affects that are often as baleful as they are positive. J.R.R. Tolkien set a standard for how to write fantasy fiction, but not intentionally so, and much of what followed in the wake of the Middle-earth stories were not just imitative of his work, but had the additional bad side effect of shoving off the table everything else with a different flavor (e.g., E.R. Eddings).
It's difficult, if not outright impossible, for a creator to control how their work is received or appropriated. Anthony Burgess was deeply dismayed for many years that his most well-known, well-received, deeply analyzed work ended up being A Clockwork Orange, which he tossed off in a few weeks. But over time he came to see what others saw in it, and why they saw what they did, even if he could not convince others that he had produced far more important things before or since. (Stanley Edgar Hyman, in his postscript to Orange, introduced me to some of Burgess's other books that way, and showed how there were things every bit as stimulating and challenging in those works as there was in Orange itself.)
If nothing else, I guess, you can at least follow in Burgess's path and try to become part of the discussion around your work. You don't have to try and commandeer the discussion, just make your case, and encourage other creators — not just fans — to take your points to heart. I sometimes think Neil Gaiman's exhortation to "make good art" (full text here) has been far more socially constructive than his actual art. And that's not because I think he's a bad artist, only that Gaiman's work (as is the work of any real original) is far more easily imitated than learned from.
Worry about someone stealing your bad ideas, because they're often the unspoken or unchallenged assumptions in your work. That doesn't mean you need to pre-emptively censor yourself. It does mean you need to speak about it when it comes up. It means you need to be part of the conversation when you can — not to shout down those who want to misconstrue you, but to nudge those just walking in away from the need to understand too quickly. The more people see you as an active participant in your own work, and not simply a passive dispenser of it, the better.