It's a question of scale. In the old internet, I subscribed to a few news groups that got tens to hundreds of posts a day. You could easily plonk the few people you didn't like.

It's also bullshit. In the old days people used to file complaints with your ISP or uni or get you removed from distribution on the server. But usually newcomers were brought in line by the community. Now, we have eternal September and it's simply not feasible to educate the hundreds of millions of people who don't know how to behave.