I've been on both sides of the coin. I've felt hurt by proxy when listening to people hating on things, but that also included people hating on people who hate on things, which previously made me constantly worry about what I can or cannot say and whether people would get mad at me for ribbing something in good humor.
I agree that "don't like, don't look" is often used to silence people who are trying to tell you something you said was hurtful, but I think it's only bad if it's impossible to determine whether you like something before you look at it.
For instance, if someone reads a book, dislikes it and criticizes it for being poorly written, that's an invalid use of 'don't like, don't look' because there's no way the critic could've known it was poorly written before reading it. On the other hand, if someone writes a scene with a graphic description of gore and tags it with 'content warning: contains gore', and then someone reads it and says it's bad because gore is bad, then it's like ... you knew it was something you don't like, so ... don't look?
I guess in general, I don't think the best way to prevent people from getting hurt is to forbid people from saying hurtful things. No-one gets to decide if something someone said 'offers nothing of value'. I think it's enough if we're upfront about what we're going to say and warn people if we know we're going to be negative, so people can easily avoid it :]