Why are the people so scared of article 17?

The answer is simple: Article 17(4) obliges all platform to prevent any copyright infringement in advance. This includes well known providers as YouTube, Facebook, Twitter, etc. as well as platforms one does not think about in this context, like WordPress, Wikipedia, Twitch, dailymotion, 9GAG, reddit and many more. Right now the only conceivable action is the implementation of general upload filters. German Federal Minister of Justice, Katarina Barley shares this opinion and wants to prevent upload filters, even though she welcomes the general concept of the copyright reform. In a limited form YouTube already implemented such a system, the so called Content ID. However only right holders have access to this system, that hold rights to a lot of frequently uploaded videos. With Article 17 such a system would have to protect every legal content of every user on one hand, but scan every upload for copyright infringements before it is published.

The effectiveness and the general practicability of such filters however is highly doubted. Those filters can not recognize the context flawlessly (is it a parody or a remix?) und faulty databases for the filters may lead to wrong filtering. Furthermore it is feared, that large platforms do not want to take this step and bypass the development of such filters by blocking content and viewers from Europe completely, leading to a simple avoidance of the European law. For platforms like Twitch, which are specialized in live streaming, this may be the only possibility. Nobody can guarantee that shown content does not contain copyright infringements during realtime broadcasts. The operators of those platforms will take some step in any case, since they are exposed to a high financial and legal risk by the cancellation of the liability limitation.

So the fear of the people lies in fear of massive cuts in the cultural freedom in the internet. They fear a loss of diversity or even complete offerings that have been part of their life for a long time. And they see a threatening restriction in the freedom of speech if satirical content can not be uploaded on established channels anymore.