I think Scanlon’s main thing, his account of moral wrongness, asserts an implausible explanatory relationship. Arguably, it says something like this: morally wrong actions are those actions that would be disallowed according to a principle of public, collective disallowing (“discouraging”) that, if followed, would not result in anyone being wronged (mistreated, abused, etc.).
This is funny at least because morally wrong actions that are wrongings of persons seem to be morally wrong because the actions themselves are wrongings of persons. Why should something like [the public, collective disallowing of an action] not being a wronging of a person be relevant to the disallowed action being morally wrong?