Disagree. His play against Beckham was as good as it gets, with the exception of that first pass. Even Pro Bowl corners aren't perfect. Other than that Butler was close to perfect. Not just the numbers, look at how he played. Beckham caught three total against Butler, including that first ball; Butler knocked down three other passes and stayed in Beckham's hip pocket through some good moves. When Beckham made his catches against Butler the tackling was great, immediate and vicious. Go watch the NFL Films clip of their battle (link early in this thread).
Agreed that Butler needs to compile a larger body of work, but he's grown since week one and is now at an elite level. As long as he does not regress he is at a Pro Bowl level now. So far his arc continues on an upward path, there's no reason to expect him to start slacking off now.