[this is not legal advice, it is my opinion]
This sentiment really bugs me and feeds into the irrational fear here (GDPRanoia). There are lots of laws that can be “theoretically” enforced that can ruin a business. There is tons of arm-chair theorizing going on here on what could happen.
In particular it bugs me cause historically EU privacy regulators never ever imposed a fine on a hobbyist and the fines usually went to Apple and Google and so on. There are numbers online about this and you can dig it up. This assumption that a forum operator acting in good faith is subject to financial ruin really annoys me.
If as a forum operator, you tell people how to download data, you anonymize on request, delete personal data on request (eg: bob uploaded a photo of himself and wants it removed) … just do the basics. Do not sell your user IP addresses and profile info and emails to the highest bidder etc and do horrendous stuff. I am pretty sure you will be ok.
Heck, if Google wants to shut down any business they can do it today. It is trivial. Get a lawyers to dig through the army of patents they have and then sue sue sue. They don’t even need to be right, they just have to cause so many legal fees that you can not afford to pay and then… bang you are bankrupt before the thing goes to trial. So… never ever start a business?
It offends me that people think that a body that is there “to protect our rights and privacy” is motivated by “shutting down every small operator out there that has one IP address stored in the database”.