When does a comments section in an online newspaper cross the line?

Here in the UK, we are unfortunate to have the Daily Mail.

If you have never come across this ‘newspaper’ before, then you have won the proverbial lottery. It is kind of known to be full of misogynistic, sexist, racially motivated comments as well as basically referring to anybody over the age of 35 as being old and should be put down like an ill dog.

But enough about the articles as this is more about the comments section.

In a recent article discussing the marches around the world against Donald Trump, one post had over 11,000 comments. Contained within these comments were a large number that were misogynistic, sexist and downright degrading towards women.

For example, ‘selfish bitches’, ‘they are all on their period together’, ‘they all have unwashed knickers’, ‘they should be at home pleasing their husbands’, ‘tarts’, ‘cows’, ‘millions of men are now going without dinner’ the list goes on and on.

Now, these comments have been left unmoderated by the newspaper (for some reason they only decide to moderate certain articles mainly about celebrities and what shoes they are wearing) so my question is this.

At what point should a newspaper be held responsible and to what degree based on the comments section? Are they correct in allowing sexist comments (or in other articles they have allowed things that would constitute hate speech) to remain?

Is it somehow different because it is online?

Discuss.