Toolbars are customizable, so you can remove the 'Toggle Filter' button from the toolbar. And of course when you launch GridView without Edit rights, you can't put it back on. This effectively prevents usage of Toggle Filter.

Load GridView with Edit rights. From the View menu, pick Customize. Go to the Commands screen. Make sure the 'File' list of buttons is selected - it is by default. Now left-click drag the Toggle Filter button from the toolbar and drop it onto this Commands screen. For this user, the toggle filter button will now be gone from the top.

It seems reasonable to have this function inactive when Edit rights are not granted, so we'll see what we can do for a future release.