See implicature and “When Truth Isn't Enough”. If there are arguments for X but they are all bad, “there are arguments for X” is technically true, but misleading, and not terribly relevant to whether X is obviously wrong.

As for the specific case of AA, I agree it's neither as obviously right as banning murder nor as obviously wrong as banning glasses (to steal examples from “Searching For One-Sided Tradeoffs” on Yvain's blog), otherwise it would either be uncontroversially implemented everywhere or something no-one ever seriously proposed (other than the kind of mentally ill dictators who ban banknotes in denominations not a multiple of 9), but to treat this as something very informative about AA is the fallacy of gray.

(There are good arguments for banning glasses: for example, kids might try to use them to focus sunlight to burn ants and accidentally burn their own skin instead. It's just that arguments against banning glasses are much stronger.)