I didn't said it "couldn't" be done. I might have said I won't do it, or that it will be difficult. The issue I believe was having to scrape your entire history of tweets to find those that retweeted account: x
infact IIRC, I think I said you can already do it with a few steps: scrape / action.
however, thinking about it on a clear headed sunny morning, if we just include "unretweet BOT retweets of account X", then we can use the internal database, *IF* the retweet stores:
a) the profile URL / ID
b) the tweet URL
as there is no need to scrape all tweets...