Yes, a Mason can be liable to Masonic charges for belittling the Worshipful Master behind his back within the lodge. According to the ancient charges of Freemasonry, it is stated that "no Mason shall slander another behind their backs, to impair their temporal estate or good name". This principle emphasizes the importance of maintaining respect and brotherly love among members, particularly towards the Master of the Lodge, who holds a position of authority and respect.
Furthermore, any violation of Masonic obligations or established laws can be considered a Masonic offense, which may lead to disciplinary actions such as reprimand, suspension, or even expulsion, depending on the severity of the offense and the outcome of a Masonic trial.
As noted in the Constitution of the Grand Lodge of Texas, "every violation by a Mason of his Masonic obligations, or of the established laws, usages, and customs of Masonry; and every violation of the municipal law, involving moral turpitude, is a Masonic offense".