XF 2.1 Prevent guests using INSERT > Image and hotlinking images to image proxy

[RallyFan]

Hi all,

Just wondering if there is a way to stop this?

I've stopped them dropping links (both pasting and INSERT > LINK, and in a message as text), however they can still go INSERT > Image and post an image that way.

When they do the site image proxy (proxy.php) picks it up and allows it to be attached.

Any ideas how I can all guests to literally post text only?

Preferably without more addons as the sites ready to go apart from that.

Thanks