The fact is there is only a few, one or two, studies out there that deal with second-hand vapor. There are no, repeat, no long-term studies done at all. And when I say long-term, I'd be willing to accept a study done over a 6 month, 9 month, 1 year, etc, (which is not exactly long-term, but still something like that is better than a 3 hour study), timeframe, as vaping hasn't been around all that long. But again, there are no studies like that out.
The numbers the OP had used in his theory are flawed slightly. I do know that size matters here, the size of the room, the number of vapers. 1 person vaping 1ml an hour is high, per the OP, but what about 10 people vaping .1ml in an hour? I'm pretty sure I can vape much more than .1ml an hour, and I've only been vaping for about 6mos. If you have 20 people vaping even .1ml an hour, the OP's numbers just doubled. If those 20 people vaped .2ml per hour, quadruple. Point is, you can't pick and choose the numbers you use, and expect that it won't get challenged.
The OP's theory is based on math of one person vaping in a small room, over a period of 3 hours. This is not repeated exposure, just one time occurrence. Scientifically, how can we honestly say that is an absurdity to see second hand vape as a public hazard in anyway, even in a tightly confined space in the long-term when studies have only been done short-term?
I'll be 100% honest here, you want proof from me that second-hand vapor is harmful, I can't provide that, as no studies to my knowledge have been done that cover the long-term.