Establishment Clause Violation Via Twitter?

On Monday, the Freedom From Religion Foundation (press release) wrote a letter (full text) to Wisconsin Governor Scott Walker claiming that a "tweet" he posted to his official Twitter and Facebook accounts violated the Establishment Clause.  The tweet read "Philippians 4:13"  The Biblical verse referred to reads: "I can do all things through Christ, who strengthens me."  In requesting the governor to delete the message, FFRF said the quote seems more like "the utterance of a theocratic dictator, than of a duly elected civil servant." It went on:

As governor, you took an oath of office to uphold the entirely godless and secular U.S. Constitution.  You have misused your secular authority ... to promote ... one religion over another....

The posts have not been removed. [This is a correction. An earlier version of this posting incorrectly stated that they had been removed. [Thanks to Bill Dunn for the correction.]]