The reason that selective enforcement exists is that it is very hard to avoid having rules selectively enforced.
But the history of selective enforcement strongly suggests that it does not usually lead to just results. It is often instead something that unaccountable officials find themselves easily able to exploit for questionable purposes.
For a notable example, witness how selective enforcement during the War on Drugs was used to justify mass incarceration of blacks, even though actual rates of drug usage were similar in black and white communities.
Yes, I would argue that it would be better for more to have been incarcerated, for that would bring greater focus to injustice and the law would be changed. Selective enforcement interferes with the feedback mechanism that would otherwise make the law work better.
But the history of selective enforcement strongly suggests that it does not usually lead to just results. It is often instead something that unaccountable officials find themselves easily able to exploit for questionable purposes.
For a notable example, witness how selective enforcement during the War on Drugs was used to justify mass incarceration of blacks, even though actual rates of drug usage were similar in black and white communities.