Because I've always been the kind of person that says what I'm feeling. Sometimes what I'm feeling isn't "nice." I'm not asking for everyone to agree with me when I say Spider-Man 3 is a fucking awful movie, and I'm not asking for it when I say I don't like a certain band or album. I'm simply stating my personal feelings on something. If all I ever did was talk about what I did like -- then there would be no basis for comparison. You'd only be getting one side of my personality and musical taste.
I don't think that's very authentic. I don't think that you can really trust a 'yes-man.'
I don't cook 5-star dinners either ... but I still have an opinion on food. The idea that one needs to be better at something in order to offer their thoughts on it, makes no sense to me. That said: I've made something to be judged. You're using it.
I don't think you should withhold criticism but a lot of the time I see you post negative things it's consistently in a way that looks like you're just outright trying to be mean. It's easy to look at a mainstream piece of media like Spider-Man 3 and say "Oh, that sucks" because 1, it's got such a large team behind it that it's not really a personal attack, and 2, it's so widely known that an individual opinion is pretty insignificant. When you're talking about a small independent release like this, though, you're one of only a few people commenting on it and things stand out more. I disagree with the notion that "if you don't have something nice to say don't say anything" but from what I've seen on this website you could stand to be less insulting with your criticism of tiny projects like this. If someone I knew posted solo material on facebook, I wouldn't comment "this isn't good," I would maybe tell them my thoughts on it privately to help them improve. Criticism should be a tool to help people fix what's wrong with their art, not an outlet to bash it.
Obviously it's your website though, so you're gonna do what you will.