You missed one point there. The questions surrounding enforcement priorities are completely invalid if the issue at hand is bad policy (especially if it runs counter to the public good).
While arguments about enforcement priority are interesting in cases where a given law serves legitimate public interest, they are a reeking red herring when that is not the case. A "good law" can be effectively unenforceable if the cost/benefit ratio of that enforcement is high enough.
However, this is not a "good law."
DMCA is very bad public policy. It creates a huge incentive for companies to attempt many abusive forms of "vendor lock-in" and criminalizes many creative ways in which people might attempt to use and modify devices which they have purchased.
To strain the widely over-used automotive analogy a bit here is as if there was a law making it illegal to pick or otherwise circumvent a padlock. So car manufacturers start putting padlocks on the hoods of their vehicles and keeping the keys. It clearly does not serve the public's legitimate interests to keep people from choosing their own mechanics, their own brands of spark plugs, oil, and so on. In fact it would be considered an absurd injustice to arrest and try someone for cutting the lock off his own car. Beyond that the very notion of someone buying a car but being locked out of it ... and for it to be a criminal offense for him or her to gain access to his own property ... is absurd.
All efforts to do this with software are ultimately doomed. However, the effort has done tremendous harm to the public ... and will continue to do so until these policies are changed and the DMCA, in particular, is repealed.