Saving Wesley is just the same as when some rich or powerful guy's child is caught in some offense and doesn't have to serve what some guy of the street would have had to serve.
If no senator or congressman ever experiences the law as unjust, they will not be willing to change it, because they don't see what is wrong with it if they are exempted from it - of course, this doesn't directly apply to that TNG episode as Picard didn't make the law, but still it doesn't mean that laws shouldn't be absolute.
The moral one should take home instead is that laws, while absolute, need to be proportional: murder is worse than accidentially stepping into the flowers or infringing on copyright, thus murder should carry a heavier penalty than the others.
Provided, of course, one buys into the idea of punishment instead of prevention: If one wanted the crime not to take in the first place, you cannot be fixated on revenge, which only causes a cycle of fear and violence, but instead on understanding the causes to uproot them. For the US, for instance, this would be repealing all copyright law except for expressly commercial infringement of significant size and instead introducing social security so that starving artists don't starve.
From this it also follows, by the way, that one shouldn't use the death penalty - except maybe for government officials - as a punishment, as it only continues the cycle of violence.