All I have to say is, I started running small engines in the 1950s, and driving and working on cars and stuff since the 60s.. I only started seeing rotten dissolved mush lines and gaskets since the introduction of ethanol into fuel. I saw old and cracked lines that needed replacing, but I never saw a glob of what used to be a fuel line, never. I also remember the first big wave of adding ethanol to fuel during the oil embargo and crisis years, thousands of vehicles suffered from it, there was a big outcry, it was in the news and stuff. Perfectly sound fuel lines were destroyed within months of use. Carbs, and this was the era before fuel injection was common, were totally gummed up. Coincidence?
All the big manufacturers have distinct warnings on their small engine stuff to not use above e10, all the ones I have seen, albeit I haven't looked at anything new for a few months now. Are they all mislead, all their engineers and studies wrong? All the major car companies have sent letters to the feds saying they can't handle the introduction of e15, they oppose it (outside of designed for it flex fuel vehicles of course). The machines they have built in the past that are still on the road by the miillions that can handle e10 won't handle e15 very long. Their analysis is all wrong, and you are right, that the alky is harmless? If these dissolving and rotting lines were caused by a different additive or component of gasoline, why wouldn't they say so? What do they have to profit by saying it is the addition of alcohol which has caused the problems? If it was another chemical, they would *say* that, if that is what they thought.
Oh, my genny, not sure how old it was at the time, not ancient, not new, never checked, ran fine for the few minutes when I tried it at the shop when I bought it, then ran for a few minutes here. From the *outside* the line looked fine, seemed perfectly sound, but after a few minutes of sustained vibration, the rubber thick grommet gasket just fell off. I missed it, the tech at the shop missed it. Our bad. On later inspection, it was like...putty, just a glop, you could push it around with slight finger pressure. It was mostly dissolved, just intact enough to stay together as a glob. And the inside of the rubber fuel lines where chunky styled, breaking off in soft globs as well. It wasn't like an olden days pre ethanol grommet or line where they just dry out and crack or shrink a little, this was some sort of chemical dissolving action going on.
I absolutely *never* saw that sort of failure in the past with any sort of fuel lines on any machine. This is all new since the introduction of ethanol. Now in the past, pure gasoline with no ethanol was prone to excessive varnishing and gunking up if it sat around a long time..but it still didn't dissolve lines and gaskets. And I am assuming gasoline had the same chemicals in it as in your list above, back then, as it does now. What is different now is ethanol. So either it is the mother of all coincidences, and all these manufacturers are slap wrong, or ethanol really is the culprit.
I am afraid I will have to invoke Occam's razor on this one as per my opinion.