I see little wrong with this. I understand the idea that it's not necessarily right that ad companies stop supporting something based on ill-defined criteria, and I do support the idea that the criteria should be well defined. In this case, I think the criteria is pretty well defined: "pattern of speech that could incite violence or discrimination against a minority group." Although the site says that they, "have always and continue to condemn racism and bigotry in any form," their actions, in this case articles like, "Why There Ought to Be a Cap on Women Studying Science and Maths"[1], doesn't reflect that message and this in particular is discriminatory against women. There are other examples in the BBC article as well. The BBC article also mentions that the articles in question were written by a guest author, not a staff member, but the onus on posting something on the website falls on the staff, so that argument falls flat.

The other and simpler reality is that they are a private company that can do what they want when it comes to how they utilize their resources. If they don't want to serve ads on Breitbart then it's their choice. Even if they just arbitrarily chose to disallow Breitbart on their platform, it might be unjust but it's their right and choice.

On a more philosophical note, consider that all these issues of "fake news losing ad revenue" and the one mentioned here are generally only possible because the media is very free to post whatever they want and get paid for it, thanks to the USA's extremely free media laws. It isn't ideal for sure, but in some respects I'd rather have this reality where we worry about a specific news organization losing ad revenue than the reality where the only news that I can read is state sponsored.

1: http://www.breitbart.com/big-government/2015/06/15/heres-why...