I know this is an old thread, but I have the same question. Has anyone ever found a way to do this? Specifically with Outlook 2013.

I found something that seemed to indicate that the people you didn't want responses from could be added as Resources and those people would not be able to send responses.
https://support.microsoft.com/en-us/...est-in-outlook

I also found this article about BCC people in a Meeting Request that says if you don't want "a person's name to show up on the list of meeting attendees, you can add them as a "Resource" in the request."
(It also warns that "doing so will add their name to the Location field for the meeting." But when I tried it, Outlook asked me if I wanted to update the location and by answering "No", the names were not added.)
Add Bcc recipients to a meeting request - Outlook

When I tried this, however, the people listed as Resources were still able to send responses, and many did.

If anyone has any insight, I would greatly appreciate it.

Thanks,
Kevin