Yeah, I have to admit because this was my first work I maybe overdid it in providing references because I wanted to default to having real historical data and not just writing a lot of personal opinions with no backing (it was a nightmare writing up that reference section but I'm glad I did it in the end) and if I'm being honest, because I'm not in academia and didn't have credentials as an "Estonia expert" I wanted to play it safe.

Edit: Added some context and I'd also mention that one thing that was quite helpful is that at the start of the writing process I created a massive spreadsheet where I'd add in quotes, writing, and anything interesting I thought I might pull from (some of it manually written, like when watching documentaries). This was hugely helpful when I was going back but also during the writing process so I had a single source of truth I could keyword search. I've just checked it and its got 4787 rows, with most entries being about a paragraph long

It sounds like you did the right thing and that guy is grumpy.