He was pointing out that you mixed your units in your analysis. You divided annual cost by daily ridership for the cost instead of multiplying the daily ridership for annual ridership. I think he was short in how he pointed this out to you. That being said, as the one presenting the data I believe it's in your interests to ensure that what you wrote is accurate. When someone shows inaccuracies, I think it's disingenuous to continue to use data that has been shown to be flawed. That was more tersely expressed as "you should take it down."

I would recommend changing your units in your site to either be all daily, or all annual. This means that you could meaningfully present and compare percentages of ridership, like I did for ATL above.

Getting back to the numbers at hand, YUL has 82% O&D[0], meaning that for 15M passengers there will be (15m * .82 / 365) -> 33,298 daily users. 30% daily ridership does seem like a steep target to hit. If you get the O&D numbers for all of the airports and compare daily values, you may still be able to express you idea and make a case without people being distracted by inconsistencies.

Another factor to add, eyeballing your graph, would be the correlation of metro ridership to the percentage of airport passengers opting into the metro. The numbers for the southern US would probably be explained by a poorer metro compared to SF and the northeast.

You put yourself out there, and you obviously are passionate about your subject, but please take a step back to look at the suggestions and how they will improve your case or show you new insights.

[0] http://www.admtl.com/sites/default/files/RA2015_A.pdf "The percentage of connecting or transit traffic held steady at about 18%, i.e., nearly one in five passengers, or 2.8 million people for the year, had an airport of origin or destination other than YUL."