Apparently you're missing the part where "chemtrails" are a
conspiracy theory.
This means there are people who believe they exist, despite all evidence to the contrary.
Until "chemtrails" are proven to actually exist outside of conspiracy theory, then they don't exist. The theory exists, but it just that, a theory.
http://en.wikipedia.org/wiki/Bigfoot
http://en.wikipedia.org/wiki/Loch_Ness_Monster
Conspiracy theory is a term that originally was a neutral descriptor for any
conspiracy claim. However, it has come almost exclusively to refer to any
fringe theory which explains a historical or current event as the result of a secret plot by usually powerful
Machiavellian conspirators, such as a "
secret team" or "
shadow government", rather than broad social forces and large structures of human collectivities.
[1]
Conspiracy theories are often viewed with
skepticism and sometimes ridiculed because they are seldom supported by any conclusive evidence and contrast with
institutional analysis, which focuses on people's collective behavior in publicly known institutions, as recorded in scholarly material and mainstream media reports, to explain historical or current events, rather than on
secretive coalitions of individuals.
http://en.wikipedia.org/wiki/Conspiracy_theory