A conspiracy theory is merely a theory without corroborating evidence. The reason conspiracy theorists tend to be disbelieved is that, more often than not, their assertions are a matter of faith, and when they're right, they're right in the way a stopped analog clock is right twice a day. If someone's paranoid fantasies happen to correspond to reality, that doesn't make them more trustworthy.

So while conspiracies shouldn't be dismissed out of hand, they also shouldn't be given special credence, either, and skeptics should be assumed to be part of an attempt to suppress the pursuit of truth.

That said, A lot of skepticism is as much an attempt to reinforce confirmation bias as is conspiracy theory - and one could say that conspiracy theory is a form of skepticism about the apparent natural order of things. So both sides tend to suffer from a tendency to not actually care about the truth when that truth could contradict their prejudice.