I think that his point is that, if he didn't know enough to take it to the trial, the original "conviction" (not really, since there was no trial - but in effect, enough to force the payment of fine) of him would stand, despite all those blatant issues of lack of evidence that are inherent in traffic cameras - in particular, the lack of the ability to prove that the driver is the specific person charged.

In other words, the city wanted to fine him under the "civil" rules, where they claimed simple preponderance of evidence (car being on video, and its plate number establishing him as owner, and therefore the most likely driver) - even though the infringement itself was that of a criminal law, and no harm was demonstrated to pursue it as civil. But the moment he did challenge them, then - and only then - the new higher bar applied.

Logic would dictate that either the bar should be applied from the get go - i.e. that no-one should be fined unless there's clear evidence that they were the drivers (which would likely result in all traffic cam evidence being summarily thrown out as inherently incapable of meeting that bar); or else, if we want the low preponderance of evidence bar for fines, then actual harm should have to be demonstrated for the fine to apply.