Here it looks like he is just upset because he believes that everyone should have the ability to like whatever they want.
And if that is the argument, that in itself is fine - everyone is entitled to like what they want, and they don't have to defend it. The trouble starts when you begin to deride other things (presenting your opinion of dislike as a fact) and deriding other far more informed opinions of those things. Again, I may not like The Godfather, and I'm free to say so (and, should I choose, I can offer an argument as to why I don't like it, but this isn't required because I'm merely saying I enjoy something). However, I cannot say that The Godfather is bad because I don't like it - i.e., The Godfather is bad "in my opinion," without providing an argument for your point of view. Those are two very different things.
Film scholars, critics, and audiences alike all largely agree The Godfather is one of the best films of all time and can provide a comprehensive, intelligent explanation as to why. If someone were to claim The Godfather wasn't a great film, they would have to justify that opinion (and objectively they would really struggle to).
The same can't be said for something more polarizing, like say, Avatar. Many really enjoyed the film - I'm one of them - but I can also entertain the argument that
it's not a good film because of its stock, undeveloped characters, cookie cutter plot, and excessive length. All three of those points could be expanded upon with specific, inarguable points of evidence and analysis from the film proper. I could also entertain the idea, however, that Avatar
is a good film (though probably not a great one) because of its jaw-dropping visuals, impressive world building, and new take on an old story.
It's really hard to argue that Dino-Rama, Stitch's Great Escape, and Imagination 3.0 are good attractions based on any inarguable evidence. There's a reason for that. You may enjoy them - and that's fine, you're entitled to! - but claiming it's objectively "good" is an entirely different ballgame. Same goes for not enjoying an exemplary attraction (The American Adventure, Splash Mountain) - you're entitled to that opinion - but you can't argue (very well) that it isn't good.
That's all because there are objective measures of quality that are determined en masse by professionals (of all sorts) who have more qualified opinions to set the standard.