Saying "but you can't bring hurt down to zero" is an invalid objection because it is irrelevant, and a pernicious one, because people use that form of objection routinely to defend their special interests at the cost of social welfare.

You speak of "social welfare" as if it were an objectively measurable property of the real world. In reality, there is no such thing as an objective social welfare function, and ideologically convenient definitions of it are dime a dozen.

Note the position of "social welfare" in that sentence. It's in a subordinate clause, describing a common behavior that I use as justification for taking special exception to something you said. So it's two steps removed from what we're arguing about. The important part of my sentence is the first part, "Saying 'you can't bring hurt down to zero' is an invalid objection." "Hurting people is bad" is not very controversial. You're taking a minor, tangential subordinate clause, which is unimportant and not worth defending in this context, and replying as if you were objecting to my point.

I don't mean that you're trying to do this, but this is a classic Dark Arts technique - if your goal is to say "hurting people is bad" is controversial, you instead pick out something else in the same sentence that is controversial, and point that out.

I also didn't mean to say that you are pernicious or have ill-intent - just that the objection I was replying to is one that upsets me because it is commonly used in a Dark Arts way.

I'd probably word it a bit differently myself, but I think (a) and (b) are in fact true.

Fair enough - it implies (a) and (b), whether true or false.

I say it isn't theoretically possible for utilitarianism to have more problems than any other approach, because any other approach can be recast in a utilitarian framework, and then improved by making it handle more cases. A "non-utilitarian" approach just means an incomplete approach that leaves a mostly random set of possible cases unhandled, because it doesn't produce a complete ordering of values over possible worlds. It's like having a rule that's missing most of the markings.