Wearing a "POLICE" shirt to get people to give you a wide berth MAY be procecutable under the Texas Penal Code, Section 37.12 - False Identification as Peace Officer; Misrepresentation of Property.
If people passing you on the road believe you are an LEO, and by admission you are wearing it with that implied intent, then do not be surprised if the real police stop and question you and possibly charge you. Then you can cite the 1st Amendment to them and the judge. Good luck.