Alright. I'm gonna wade into this one now.... If the officers were on duty at the time the photo was taken (and presumably while they were drinking) then absolutely. Fired. Heck, the company I work for, we're not allowed to drink within 8 hours of the start of our shift. One of those silly little things where if we're dealing with people's lives, we're not supposed to be impaired by alcohol or mind altering substances. I would expect the same standard for police officers.
If they were off-duty at the time, they did show a little bit lot of poor judgement (alcohol, duty weapons, scantily clad waitress, etc), but unless the dept has specific rules regarding off-duty behavior, then in my opinion they shouldn't have been fired.