Downers
Few things make me angrier than people who like to dump on the plans and dreams of others.

There is giving constructive criticism (which my profession is built on), and then there is finding it enjoyable or personally validating to enumerate all the reasons why a project is doomed to fail.

Doing something worthwhile is hard work. "The Secret" is crap, but some mental energy focused on defeating obstacles goes a long way.

Policy based on irrational intolerance or beliefs
Included in this are:

Invalidating other people's marriages because of personal feelings about same-sex relationships.

Denying access to any medically safe health service, emergency contraception for example, because you think your moral code outweighs the ability and rights of other people to assess their own health needs.

Racist immigration and labor policy.