Old King Cole
Yes it does reduce the instances of an offence by making an act illegal. In some cases it can stop it. Look at the publicity surrounding this case, any pilot/ATCO/Engineer reading about this is going to have a little think before drinking near to the time they fly/Control/Use a spanner. If they don't? Well more fool them.
Regarding Treason, you are talking about terrorism, a different subject, which I am not going to debate on this thread. The point being that Treason is illegal. One person (to the best of my knowladge) has been convicted of an offence under the Treason Acts in the last 30 years. As far as I recall he is also the only person who has been charged. In other words there is vertualy no treason, therefore, by your standards there is no need for law against it. Alternattivly you could say that because the penelties for treason are so high, then that deters people from committing it. The same could be said of this law.
I-FORD
Unfortuatly ignorance is no defence. It is mitigation, and does not seem to have been used by this chap. As far as I am aware there is an equivilent offence now in many countries, including Finland. In fact there must have been if he was arrested on the aircraft( I wont go intot he civil aviation ammendments act and its effect on juristiction on offences on non UK registered aircraft)Your suggestion is therefore flawed. As indeed is your suggestion that this law is for the gratification of law makers/enforcers and the courts.
NN
You have summed it up, yes for that offence you get 6 months in a 'scum filled' prison. Odd thing about prisons they are full of people who have been convicted of criminal offences....As this pilot has been.