I see this as a miniature version of the extremely worrying argument about plea bargaining, that it is necessary because the courts couldn't handle the huge volume of trials that would be required without it.
If you're handing out so many violations that you can't handle everyone engaging in an active defense against them, then you're doing something deeply wrong, and the solution isn't to discourage people from exercising their legal rights.
Yes, we all have an interest in parking space being appropriately regulated, but we all have a much greater interest in the state's punitive power being appropriately exercised, and I'm sure there are ways to achieve both anyway.
I also just want to point out, the SFMTA has brought this on themselves. If they didn't have such an egregious erroneous ticket rate, Fixed could never be profitable. They only get paid if you don't have to pay the ticket, so if the SFMTA had an error rate of 5% rather than 33% Fixed wouldn't have enough to work with.