Website operators are being asked to feed LLM crawlers poisoned data by a project called Poison Fountain.
The project page links to URLs which provide a practically endless stream of poisoned training data. They have determined that this approach is very effective at ultimately sabotaging the quality and accuracy of AI which has been trained on it.
Small quantities of poisoned training data can significantly damage a language model.
The page also gives suggestions on how to put the provided resources to use.
For the same reason copyright and licences exist. You may be able to interact with something - because that’s what the license allows you - but still not be able to use it. Companies have faced million dollar fines for using code not subscribed to a license which allows them to do that. You may face trial if you distribute content (e.g. movies or music) you are only allowed to watch. The key here is that unless you are explicitly permitted to use something further it is considered illegal and punishable. Why would it be any different for AI training?