Steemit is a blog where you can post anything. Do you? No you can't.

Why can't you, you have just posted what you wanted, you can post whatever you want, you can even spam and nobody can STOP you. I think you confused Can with Should and Can't with Shouldn't.

I understand that if you post things that can be considered spam

Banner ads of any kind
Referral links/codes
Repeating the same post
Links to known scams, phishing sites, and other dangerous links
So who decided this?

Please show me this in the Steemit terms of service? Where are these rules written?

You don't understand, you believe that there is some kind of authority over the rules and someone could point you to such an authority, yet people can CURATE content as they wish, you have expressed exactly that, where is the rule that you can DOWNVOTE anyone who DOWNVOTED you? O yeah you cannot can you, especially if they don't have ANY FREAKING CONTENT TO DOWNVOTE LMFOGTFOLOLSTFUAFK.

Maybe I give this right to some to decide what is ok and what is not.
But there are some people on the pic that are posting the picture, link and a copy of the post that they copied and postet.
So who give the right to this people? That is plagarism or is it not?

Yeah, again, speaking as if some authority or centralized rules existed. Why would you suppose this, why would you believe such a thing, is the obvious implication of DECENTRALIZATION not clue enough?

So in future. If there is not a legal steemcleaner downvoting my post. If I see a person that I described that is downvoting me.
Be sure that my page will be changed to DownVotingMF and be sure you will be downvoted to. Eye for an eye.

Petty threats on the internet are much lololololol. If you downvote me I will downvote you because eye for an eye. Perfect, just wait until you are downvoted by a bot that has no posts for you to downvote, then you can picture me and imagine how funny it is for me.

If I were you I would ask/confront the accounts downvoting me and understand why it's so, but that would mean I care what people curate content as, hence "if I were you".

You can try to issue your petty threats of "retaliation" but you have to consider that you're not doing much more than "retaliation" (slave to the acts of others and responding in kind to such acts) while they in fact are doing what downvoting is intended to do or express their opinion of content, curate content as zero value.