I certainly agree that Pinside is not the most positive place for pinball out there, but at the same time, I can't really condone blocking someone or having them ejected just because you only want positive comments that totally agree with your opinion.
If your opinion is so weak that it cannot counter any resistance, it's not much of an opinion at all.
I used to absolutely loathe all Gottlieb SS games and I only liked WMS games, but thanks to people championing them, I actually enjoyed playing some Genesis at the last couple of shows and find things to like in many other Gottliebs these days. That only happened because the opinions of others were strong enough to counteract my own opinions.
The idea of an echo chamber where people only parrot the same opinions back and forth is kind of boring and repetitive.