You are absolutely correct that piston motors can create contrails as well, it can happen in any engine that uses air in the process, even cars when first started can leave a little vapor trail before the exhaust pipes get really hot.
You mention the "law of unintended" consequences, do we really know if they are "unintended"? Remember back; there has been a lot of talk about population control, are these things part of that plan in action? Pretty convenient way to eliminate some while trying to save even more maybe?
I have a few less thought provoking daily doses coming up, so you don't need to worry.
Thanks for your continued support,