I get tired of seeing people whinge about how a cop that pulled them over, should be catching real crooks. (NEWSFLASH - you broke the rules - like them or not)
As you point above, a cop on traffic duty IS doing as he/she is supposed to be, and like any other organisation/group, cops have different divisions/sections. Traffic being one of them. (amount of resources devoted to the various sections is not up to the individual cops)
While I acknowledge there are cops out there with bad attitudes, they are in the monority (in my experience) and generally speaking, if you give them respect, you shall receive.

Personally have a lot of respect for the job they do, especially give they way they get treated by the public sometimes.