The important thing to realize is that once you have release something, you have no control over how it is used. It doesn't matter whether it is an open source license or a commercial license. You have the right to take legal recourse, may that be over copyright infringement or licensing terms, but that requires both the means and desire to pursue what may be a lengthy process with an uncertain outcome. Worrying about stuff you cannot control is going to have a far more negative impact upon your life than it will upon those who are using your software for evil.

So what can you do?

Learn how to set boundaries. If a corporation demands something that you have no interest in providing, tell them no. If you are interested in providing it, request compensation for the work or request they submit a patch or let them wait until you can do the work on your terms.

For honest leechers, choose a license that discourages them. Switching from a MIT style license to a GPL style license won't prevent people from profiting from your work, but it will discourage those who want to make proprietary extensions to your work. Also realize that this won't stop dishonest leechers.

Continue to voice your concerns. Corporations don't feel guilt, but people inside them may. Even if the people within them don't feel guilt, they may still see you as an unreliable developer to exploit.