I fail to see in the Constitution where any one citizen has greater First Amendment Rights than the next citizen.
However, theft is theft and it does not matter if one steals a car or a flag, it is still against to law.
Exactly, so what is your problem with the vet's expression of his freedoms?
However, theft is theft and it does not matter if one steals a car or a flag, it is still against to law.
Fine, I'd make restitution for the property ... in pesos. See how useful the guy found them...
Just because he may technically have the right to fly another flag above the United States flag (in the US mind you) doesn't make it right.
You could also argue that by removing the offensive display the vet was actually doing the businessman a favor. There are a whole lot of people that would take even greater, ah, "offense" at such a display and said business man and/or his establishment, employees, and customers might be in some danger. So the vet was simply preventing an ugly situation.
Or how about this consideration. In many places you cannot fly the Confederate flag (at all) because it is offensive to some people. Fine, flying the Mexican flag is offensive to me, particularly displaying it above the US flag. See where the "thin-skinned, lets not offend anyone" mindset gets you? Pretty soon there will be no displays of any kind allowed. No nativities, no flags, no team logos, no historical displays, zip.
The madness has to stop somewhere, and common decency and respect for the flag of the country you are in is a very good place to start. If the businessman wants to have his own little slice of Mexico fine, he can set up shop - in Mexico. This is the USA.