"Old retirees, surly and unhealthy locals, and inconsiderate tourists" also describes a lot of New Hampshire unfortunately. Manchester is probably good for your age range though. As far as your politics go, nobody cares unless you make it your personality or when it comes to dating.

Manchester is fine. It has its good and bad areas. I haven't lived in big cities elsewhere but I've worked in the worst areas of Manchester and assume they're not as bad as the worst areas in places like NYC, LA and Chicago.