I had an interesting discussion about that with some professors as well. It might not be as bad as on the internet, but it does happen, in both research and instruction, to some extent. One prof I know pretty well, who's a good teacher, was lamenting that his students seem to actively want him to be definitive and un-nuanced. His tendency, which he has to work against a bit, is to qualify statements by noting where his views aren't shared by everyone in the field, where he's speculating past the established results, where he's pretty confident of an approach but there are arguments for alternative approaches, etc.

But students tend to interpret that as weak and muddled, and prefer profs who "tell it like it is", even if that means in a fairly biased and opinionated way. It seems they particularly like it when you make black-and-white statements that would be controversial, roughly equivalent to "there's a debate on this but you don't need to know about the other viewpoint because it's wrong".

This is not limited to the internet. We learn as children that persuasive writing is weakened by statements such as "I believe", "in my opinion", or "in my limited experience". (I believe that) it is true that such statements weaken writing, and that it should be the reader's job to determine which content is editorial and subconsciously insert the "in my opinion"s where appropriate.

Having said all that, it does seem hard to find intellectual honesty on the internet, but I had more trouble finding a decent newspaper in London so it's not an isolated problem.