And in this case, precision in terminology is vital. The police are required to respond to 911 calls - that's what they do. They get 911 calls about all manner of things and, for the most part, respond in a professional manner and respect the rights of citizens. The idea is that the police officer is there to INVESTIGATE the circumstances at the scene - it is not a presumption that a crime has been committed and that, therefore, an arrest must or even can be made.
The police officer is free to speak to a subject - free to ask questions and even to ask the subject if he wouldn't mind removing the firearms from his person and, say, putting them on the trunk of his car - but the subject is free to decline to do so. Absent the LEO's reasonably articulable suspicion, he's also free to go on about his way. What was the LEO's "reasonably articulable suspicion" in this case? Ummm...something about the rifle being "rudely displayed." Try as I might, I find no reference to courtesy in the Texas statutes.