I'm not sure what the parent meant by "beware arguments against utilitarianism" - there is nothing wrong with arguing for or against utilitarianism. It's a popular moral philosophy.
You should beware of bad utilitarian arguments though, which is where you often get the real "gotta break a few eggs to make an omelette" kind of arguments that justify all manners of atrocity in service of some narrow hypothetical future good.
Like when Marc Andreessen says we should consider anyone who would do something to slow down or regulate AI advancement murderers of future humans. Bad utilitarianism right there.
Proper utilitarians are concerned with the net difference between all positive and negative consequences of actions.
People often think they have mic-dropped utilitarianism by saying things like, "Oh, so if two people get a lot of joy by beating up a third person, that is ethical because it is overall net positive?"
A few things wrong with that. First is there is no net happiness formula which utilitarians are proposing. Peter Singer has said more than once that he weights suffering far, far higher than happiness.
Second is that every ethical system has screw cases which make the system look messed up. "Do unto others..." it terrible if you are talking about masochists.
You should beware of bad utilitarian arguments though, which is where you often get the real "gotta break a few eggs to make an omelette" kind of arguments that justify all manners of atrocity in service of some narrow hypothetical future good.
Like when Marc Andreessen says we should consider anyone who would do something to slow down or regulate AI advancement murderers of future humans. Bad utilitarianism right there.
Proper utilitarians are concerned with the net difference between all positive and negative consequences of actions.