You can already measure where the visitor's view is and notice the sections at which the visitor stares the most.

The scenario you've given is also very similar to a scenario in which the user opens the web page and then manually searches for "cancer". Or scrolls down rapidly until they notice the word "cancer" and then stops. I do that all the time for example.

So I don't see how excluding such a feature protects the user in any way compared with the status quo.