Wikiquote says this is NOT Mark Twain:

How anybody expects a man to stay in business with every two-bit wowser in the country claiming a veto over what we can say and can't say and what we can show and what we can't show — it's enough to make you throw up. The whole principle is wrong; it's like demanding that grown men live on skim milk because the baby can't eat steak.

This was actually Robert A. Heinlein in The Man Who Sold the Moon (1950); this may be the origin of a remark which in recent years has sometimes become misattributed to Mark Twain: Censorship is telling a man he can't have a steak just because a baby can't chew it.