Do I need negative ratings for posts/votes?

Question

User interface

We write CMS. It has topics and a comment system. For a very long time I have been puzzling over whether it is necessary to give the opportunity to downvote posts? A question of pure psychology. On Habré, you can minus and it seems like this contributes to the breeding of srach. There are no cons and it seems to be very convenient without them.
Can anyone give a really strong argument in favor of having only pluses or pluses and minuses?

Answer 1

What do you think of the dislikes on Toaster?
Read, there is a huge list of arguments for and against.

Answer 2

I also asked this question not too long ago. Only in my case there were not posts, but such "link cards" to different sites, it was necessary to somehow display the rating. Initially, the rating was + and -, then it was remade into a rating with stars, from 1 to 5, but, I don’t remember for what reason, I also refused this option. Now there is only a positive rating (I used the idea of ​​Facebook and VKontekte, people are already used to likes), and if you don’t like the material, you can simply hide it (as an additional option to hide, choose one of the reasons for hiding)
I saw it on some site "rating" in the form of a small graph that displayed the "readability" of the article over a period of time (probably from the date of the post to the current date). Looks interesting and quite informative.