"With great power comes great responsibility." - as once Uncle Ben said to a Spiderman ;-)

It's not that simple. There's a language barrier that might keep us to communicate effectively but nonetheless I'll try to quickly tell you what I mean.

All the content reward (author and curator) comes from the inflation. Reward pool is a common good that we are supposed to distribute to the best content. And to do that we both need up votes and down votes. We need that to collectively reach consensus on who gets what big piece of a pie. We will always disagree on what's good and what's bad content, because some people like pictures of kittens, some people like poems, other like travel blogs. Also, there are many people that are lured here by an "easy money" and they will spam with whatever content just to get rewards out of the pool. Without downvotes, you can't do anything about it and that would be unfair to the others who create good content and yourself, because reward pool is our shared, common good.

Everyone should up vote AND down vote honestly, up to their own point of view.
Up voting bad content is wrong. Down voting good content is also wrong.
If you see post that you think that it's worth more than it already has - up vote i, but if you see post that you think it's worth less than it already has - down vote it. It's not a crime, not bad feelings, it's a tool to collectively evaluate value of content on the platform, so posts that adds more value to the system are rewarded (such as original, high quality stories, etc.), while bad, low quality, low effort content that nobody wants to read is not rewarded. Because - again - reward pool is our common good.
It's NOT free money. We all pay for that, and STEEM falling down in price is a price we pay for bad choices.