The reality is rational people do dismiss hypotheses completely unsupported by the available evidence. They just at the same time acknowledge that they could theoretically be wrong.
There's nothing irrational with saying; "Aliens did not build the Pyramids", or "I know that aliens did not build the pyramids". It is assumed that a rational person acknowledges an infinitesimally small possibility that they are wrong in stating such a fact, but the reality is, all claims whether negative ("There is no conspiracy") or positive ("There is a conspiracy") are accepted by a rational person with such an acknowledgment of varying importance, so there's no reason for a rational person to append every statement with "but I could be wrong".
The crucial flaw I think that you (and the many, many others who have made such arguments) make is a fallacious distinction between positive and negative claims.
Let's take a positive claim like: "There is a chair in the corner of the room". This claim, however, well supported by physical evidence (our rational subject has felt the chair, seen the chair, and seen others interact with the chair), can't be known rationally with absolute certainty- of course, there's always the possibility that some sufficiently advanced technology, conspiracy, mind-altering substance, or intelligent being is deceiving the rational subject, and there is no chair. This remote possibility must be acknowledged, but at the same time, it is dismissed by every rational agent, and rational agents do not base their actions on such possibilities. The point is, every positive claim like "There is a chair" can be framed as a negative claim like "There is no force or phenomena deceiving me into believing there is a chair". Thus, if your suggestion that "dismissing unsubstantiated negative claims is irrational" is accurate, it would follow that you also cannot accept any positive claims without being irrational.
Rationality is having an open mind, accepting the most likely conclusion based on the available evidence, and properly estimating the degree to which you may be wrong. It works exactly like that for both positive and negative claims.
I hope you realize this isn't just semantics. This difference is crucial in understanding why arguments like "You don't know for certain if there's no God" and "You can't prove there's no conspiracy" are flawed, and these arguments are actually used by irrational people to justify all kinds of nonsense.
There's nothing irrational with saying; "Aliens did not build the Pyramids", or "I know that aliens did not build the pyramids". It is assumed that a rational person acknowledges an infinitesimally small possibility that they are wrong in stating such a fact, but the reality is, all claims whether negative ("There is no conspiracy") or positive ("There is a conspiracy") are accepted by a rational person with such an acknowledgment of varying importance, so there's no reason for a rational person to append every statement with "but I could be wrong".
The crucial flaw I think that you (and the many, many others who have made such arguments) make is a fallacious distinction between positive and negative claims. Let's take a positive claim like: "There is a chair in the corner of the room". This claim, however, well supported by physical evidence (our rational subject has felt the chair, seen the chair, and seen others interact with the chair), can't be known rationally with absolute certainty- of course, there's always the possibility that some sufficiently advanced technology, conspiracy, mind-altering substance, or intelligent being is deceiving the rational subject, and there is no chair. This remote possibility must be acknowledged, but at the same time, it is dismissed by every rational agent, and rational agents do not base their actions on such possibilities. The point is, every positive claim like "There is a chair" can be framed as a negative claim like "There is no force or phenomena deceiving me into believing there is a chair". Thus, if your suggestion that "dismissing unsubstantiated negative claims is irrational" is accurate, it would follow that you also cannot accept any positive claims without being irrational.
Rationality is having an open mind, accepting the most likely conclusion based on the available evidence, and properly estimating the degree to which you may be wrong. It works exactly like that for both positive and negative claims.
I hope you realize this isn't just semantics. This difference is crucial in understanding why arguments like "You don't know for certain if there's no God" and "You can't prove there's no conspiracy" are flawed, and these arguments are actually used by irrational people to justify all kinds of nonsense.