There are couple of issues here and this might very well become a meta bug:

• I believe the team wants to remove the privacy setting that lets users disable accessibility. There are several historical reasons why it was added and many of them are not relevant any more. However, the connotation of accessibility enabled being bad for privacy still exists and hurts the image.
• We need to decide if we want to hide the "Inspect Accessibility Properties" menu item in the browser when accessibility services are force disabled.
• An alternative (or complimentary) to the above is having a UI in the panel when accessibility is force disabled that lets users enable it again right from the panel.

Originally some of the issues where flagged in bug 1636831.

(In reply to Yura Zenevich [:yzen] from comment #0)

• I believe the team wants to remove the privacy setting that lets users disable accessibility.

You did this in bug 1613468 but as far as I can see, you added no alternative as suggested in the report's description or otherwise. So now users who previously disabled the feature don't know what's wrong, and the developer tools message still says "It is turned off via accessibility services privacy preference." (I suspect that's the root of the problem in bug 1683533)

(In reply to Gingerbread Man from comment #1)

(In reply to Yura Zenevich [:yzen] from comment #0)

• I believe the team wants to remove the privacy setting that lets users disable accessibility.

You did this in bug 1613468 but as far as I can see, you added no alternative as suggested in the report's description or otherwise. So now users who previously disabled the feature don't know what's wrong, and the developer tools message still says "It is turned off via accessibility services privacy preference." (I suspect that's the root of the problem in bug 1683533)

Thanks for bringing this up, I updated bug 1683533 and we should be able to update the wording around how to re-enable soon.