Well, downvoting is a clear sign of two things, one is that you dont like the person or you down like the content that he published. It could also mean attacking him. In every culture, it may have different meaning like shutting him up as like muting them so to speak.

But I come to think of this that each person and individual has different level of knowledge or skills in terms of writing/ blogging. And because Steemit is a social media, we cannot really tell someone to shut up or stop spamming. Some people who do posting, sometime they dont realize that they are making spams by the way they post, though some are actually intentionally do it. Some people who are less fortunate and less educated are actually reaching out by social media and sometimes we interpret these as spamming. Well, it is difficult to shut somebody when they think of themselves as in the right position in a social media space. Even one of them really make noise just to be heard.

But of course there is always ways to filter spams and not spams and the dev should help us on this using some kind of smart algoritm.

Still, everyone has the freedom to voice out and get heard especially that steem has always rewards for these people. Money always make sense in everyone's action.