It won’t really matter, because there will continue to be other sources.

Taken to an extreme, there are indications OpenAI’s market cap is already higher than Tomson Reuters ($80bn-$90bn vs <$60bn), and it will go far higher. Getty, also mentioned, has a market cap of “only” $2.4bn. In other words: If enough important sources of content starts blocking OpenAI, they will start buying access, up to and including if necessary buying original content creators.

As it is, while BBC is clearly not, some of these other content providers are just playing hard to get and hoping for a big enough cash offer either for a license or to get bought out.

The cat is out of the bag, whatever people think about it, and sources that block themselves off from AI entirely (to the point of being unwilling to sell licenses or sell themselves) will just lose influence accordingly.

This also presumes OpenAI remains the only contender, which is clearly not the case in the long run given the rise of alternative models that while mostly still not good enough, are good enough that it’s equally clearly just a matter of time before anyone (at least, for the time being, for sufficiently rich instances of “anyone”, with the cost threshold dropping rapidly) can fine-tune their own models using their own scraped data.

In other words, it may make them feel better, but in the long run it’s a meaningless move.

EDIT: What a weird thing to downvote without replying to. I've taken no stance on whether BBC's decision is morally right or not, just addressed that it's unlikely to have any effect, and you can dislike that it won't have any effect but thinking it will is naive.