I don't understand how you could delete messages from the receiver. Not a lot of apps, including imessage, support that.
https://github.com/drewburns/chatcleanse/ Looking at App.tsx it seems one has to download Instagram data, then the app runs a filter, reports results, then you have to go into your Instagram app and delete it. It's a MVP.
We also do this as we want to keep it all local and we thought this would be most private