Additionally: you don't have to read what people say about you. You can turn off notifications for reblogs (yes, reblogs are the only way to comment on something) and in fact, commenting on something that you disagree with will make it still louder. A reblog causes the number of Notes to increase even if you disagree with the content. So there's no good way to express your disapproval of something.

Tumblr is mathematically biased to prevent feedback from the outside. People who use it rarely change their opinions because of this.