The police sergeant in The Rising of the Moon might like to think of himself as a tough cop, but the evidence says otherwise. Thanks to his being manipulated by a terrorist on the run, we find out that he has a rather soft and squishy side that prevents him from doing his duty.
The escaped prisoner is a wily, devious old soul who shamelessly plays upon the Sergeant's sentimental attachment to his identity as an Irishman in order to trick him into letting him get away. Even when the Sergeant realizes he's been tricked, he makes no effort to recapture the fugitive terrorist; he's developed too much of a personal connection with the man to do such a thing.
A genuinely tough police officer would've done his duty in such a situation. He would've put aside whatever personal feelings he may have had, any sentimental attachment to his nationality, and done his job.
Toughness in such a scenario doesn't involve brutality or the meting out of harsh treatment; it simply means doing what needs to be done. Unfortunately, the Sergeant failed to show such toughness, and the consequences of his actions—or rather, inaction—will be paid in the blood of innocent people soon to be murdered by the terrorist he allowed to get away.