The second point I can understand. If something isn't illegal and you do it with no care in the world then the government changes the laws then prosecutes you then that's just wrong. Same with sentencing, if, say, you commit a speeding offence and expect to get a 3 point hit and £60 fine then the government introduces flogging to help stop speeding, you'd feel mightily hard done to to be sentenced to flogging when you committed the crime before the law was brought in. Hall has to be judged against the criminality and sentencing guidelines of the time he committed the offences.
It's crazy and I don't care that he might feel hard done by, the law is an ass in this case.
If instead of your 3 point fine and £60, you were hit with 5 points and £100, you'd get no sympathy from anyone if you started "But, it's not fair...". It's only introduction of the word "flogging" that makes your point. And it would be absurd to flog anyone for a speeding offence at any time.