how about in five years' time?
Will all the criminals have become nice? Will he be given roses and chocolates on the street?
If he is already entering every situation looking for the negative (as you said), then he's not likely to become a very happy little vegemite, is he?
Just exactly what do you think is going to ensure that ten years from now he's not bashing the shit out of people because he's just had enough?
I guarantee your answer will be the same as every other cop's wife whose husband eventually went on to bash the shit out of people.
Get over your nonsense and realise I'm not blaming HIM - it's the JOB.
Only a very small number of personality types are able to do that job without it affecting them negatively and you have already explained your husband is not one of them.