imageboards sure do -- poorly.
listen, some of the niche corners of that world aren't so bad, but it ain't the place to be training AI to do something, unless that something is a hate crime
So filter the content before you use it. Clearly openAI did the bare minimum on this front.
The Daily Mail (the newspaper) has been used for training LLMs in the past, yes. I don't know if it still is.