People often forget what entity coined and pushed the term conspiracy theory.They only see the word in mass-media attached to individuals or groups and take it for granted.
Even if theories said by 'legitimate'(/actual) conspiracy groups are false, that doesn't mean we're so quick to dismiss a discussion about it.Often the discussion itself is more important about the truth discussed, and in some cases people quickly change their minds when presented facts.Same goes in reverse: you cannot call someone a conspiracy-nut when you cannot disprove his claims and more over his claims gradually become accepted by society.
This is why the general public has issues with such persons or such big claims: they are not capable(or willing) of thinking some people are capable of such malice, and they're willing to dismiss even a discussion because: 1.it's uncomfortable; 2.the truth is hard to reach; both unreasonable arguments to shutdown a discussion, let alone charge someone (which in US this apparently has re-surfaced).
A society becoming so intolerable of listening to such people is the first symptom of societal collapse.You can call this a conspiracy, or just check a history book. The difference is that we can somewhat verify information more quickly now, as long as people keep their innate filter on and stop consuming garbage.