You make a valid point but I disagree regarding the rewards system encouraging people to NOT post controversial content.
People will eventually be fed up with the same "Hi, I'm a girl I like traveling and by the way, here's some bikini photos", "I made this website with beautiful graphs", "This is another average sob story" or "How to make money on steemit" posts. I, for one, already am.
Once this becomes a more widespread opinion it will not go unnoticed because suddenly such posts won't rack in $1k-$10k. I'm sure that will bring quite the revelation to the steemers, and hopefully help them realize that generic content is nothing special.
Hopefully you are right and that will bring more diversity of successful content, but I don't think it will help truly controversial (not evil, not hateful, but controversial) content.
The First Amendment doesn't say "shall make no laws regard Free Speech... unless it's hateful." Hateful thoughts will still exist, and will find voice in other ways, You can't stop it by silencing it. You can only educate, and do what Gandhi suggested - be the change you want to see in the world, not force the change you want to see in the world. If you initiate aggression against hateful people, how are you better than they?
Truth. Thank you.