How long you been in this fandom? Or any fandom? People are going to call people on hypocrisy. In short: Bring the "A" game. Got an opinion? Great. Start citing how "X" is worse that "Y" cause "Y" is a superior product, you better be willing to back it up and then brace to get it torn down and torched.
If someone is posting their opinion on some important political issue like universal health care or gay marriage I would agree with you. I do not agree with you when it comes to frivolous things such as films. I was talking to a Star Trek fan at work a few weeks ago and he mentioned that Deep Space Nine was the worst Star Trek series without backing up his opinion. Should I have aggressively interrogated him and forced him to compare everything he didn't like to the other series? Should I then have "torn down and torched" his argument if his responses didn't satisfy me? Of course not, so why should we behave any differently on these forums?
Public forums, you don't get to say that everyone has to play the game your way. If you don't want to back up your opinion one can force you. However, people have the equal right to tear into it, and you can't force them to not to do so. When you slam something for something the rest of the franchise has done for decades, people are going to call BS and they're going to counter it and push for you to back your opinion.
You set the level of engagement, the same as the rest of us do. If you don't like defending your opinion, then don't.