I think the point is, how can you think a movie that neither you nor, at the time, anyone else has seen, is going to be bad- or good for that matter?
Flip a coin. You have a 50/ 50 chance of being right. Well, since the MCU has a pretty decent track record, maybe not but, theoretically, 50/ 50.
So the only reason these people could have for thinking the movie would be bad would be for reasons that have nothing to do with the movie itself or simply that any movie that they think will present a message or point of view they don't like is bad.
Granted that tends to be par for the course. On a scale of zero to a hundred, personally dislike the idea equals zero and personally liked equals one hundred with no in between.