it's all the same to the color-blind dog

Exactly what I was going to say. They need to get him fixed. They're putting him at a greater risk for cancer.

Having a fixed animal does not make you a responsible pet owner.

however, having an unfixed one makes you irresponsible

I'm simply saying fixing an animal is not the only way to prevent breeding.

It's not just a matter of preventing breeding. Dogs- both males AND females in my experience- get more aggressive the longer they go unfixed. Female dogs have their risk of reproductive cancer increased for every heat they go into without being fixed. Male dogs have their risk of reproductive cancer increase for every year past sexual maturity they go unfixed. Both genders have increased risk of hormone issues as they age without being fixed. Not to mention it can literally only take ten minutes of your dog being unattended for them to find or be found by a dog of the opposite sex and the female to end up pregnant. So, yes, getting your dog fixed IS inherently more responsible, because it is being proactive instead of having to go "whoops, I let my little dude get the neighbor's dog pregnant, guess I'll play dumb" or "whoops, I let my little gal get pregnant, I better start looking for places to dump the puppies once they're born." It's the same logic as to why using a condom to prevent getting an STD is smarter than getting an STD and having to go through medical treatment for it. One is inherently more responsible because you take steps to keep the event from happening instead of just cleaning up the mess.

Just speculating here, but maybe they breed their dog and that's why he isn't fixed.

#16 I agree, I just don't think it's very fair to assume OP, or anyone, isn't a responsible a responsible pet parent simply by if the dog is fixed or not. Obviously fixing an animal depends on the situation as #22 stated. I'm not saying every dog should be fixed or shouldn't be fixed.

If everyone fixed their dogs we'd have no more dogs in 20 years from now. So no, everyone fixing their dogs is not responsible.

And you're arrogant for calling someone irresponsible for not having a pet fixed. Maybe they just don't want to, maybe they eventually want to breed him or maybe they can't afford it and there aren't any vets in their area that do free or reduced spay/neuter clinics.

Cutting the poor dog's nuts off does not "Fix" anything.

And a new girlfriend

And maybe a new girlfriend too... Edit: ninja'd (I swear that reply wasn't there when I posted mine)

...and a new GF.

Or, you know, be the more responsible and better functioning human by NOT adopting a set of behaviors that is extremely harmful and toxic to both the person doing the maladaptive behavior and the victim of said maladaptive behavior. Mind games, passive aggressiveness, whatever you want to call it, the point remains the actions are at their core a BAD set of communication behaviors developed for one reason or another, and the GF (and possibly ex GF, because this would very badly damage the trust in a relationship) really needs to either train herself out of the behavior or get professional help to train herself out of the behavior. Because any sort of communication that is based on intentionally harming one of the participants to make the other feel better is unhealthy for everyone.

Yup, knew someone would bite.

I don't know which makes you the sadder person- if you're saying you knew someone would call you out on your awful "advice" to make yourself seem more "impressive" or if you actually have such a bitter personality as to have to sink to the level of baiting people with bad advice on the Internet in order to get your entertainment for the day. Either scenario makes you a rather sad being.