Why was he being "made aware" for being under arrest when what he said is completely legal.
Not legal in Texas.
In texas it falls under penal code 42.01 disorderly conduct and is an arrestable misdemeanor offense.
42.01. DISORDERLY CONDUCT. (a) A person commits an offense if he intentionally or knowingly:
(1) uses abusive, indecent, profane, or vulgar language in a public place, and the language by its very utterance tends to incite an immediate breach of the peace;
(2) makes an offensive gesture or display in a public place, and the gesture or display tends to incite an immediate breach of the peace;
(3) creates, by chemical means, a noxious and unreasonable odor in a public place;
(4) abuses or threatens a person in a public place in an obviously offensive manner;
(5) makes unreasonable noise in a public place other than a sport shooting range, as defined by Section 250.001, Local Government Code, or in or near a private residence that he has no right to occupy;
(6) fights with another in a public place;
(7) enters on the property of another and for a lewd or unlawful purpose looks into a dwelling on the property through any window or other opening in the dwelling;
(8) while on the premises of a hotel or comparable establishment, for a lewd or unlawful purpose looks into a guest room not his own through a window or other opening in the room;
(9) discharges a firearm in a public place other than a public road or a sport shooting range, as defined by Section 250.001, Local Government Code;
(10) displays a firearm or other deadly weapon in a public place in a manner calculated to alarm;
(11) discharges a firearm on or across a public road; or
(12) exposes his anus or genitals in a public place and is reckless about whether another may be present who will be offended or alarmed by his act.