Were your Consitutional rights violated? No. Were your civil rights violated? No. Because you voluntarily work there, and you consented to their search. Your rights cannot be violated if you consent. You gave them permission.
They have a reasonable concern. I think they acted a bit over the top, but they do have a valid concen. You posted videos of you and your guns (several, apparently) for all the world to see.
Some of the deranged people who have gone on shooting rampages have done the same thing.
Now that they have checked you out, and found out you are "harmless", they should do, and say nothing more about it. If they do (and especially if they say they are doing it because of some employee's worry/concern, THEN you need to talk with your union steward/HR rep, and a lawyer, as you may have grounds for a "hostile work environment" suit.
At this time, you have squat for a lawsuit. Sure, its offensive, and you were just showing off your guns, that you are proud of, but they don't know that. All they know is that your reported behavior matches that of known threat profiles.
Most companies have "no weapons" clauses in the employee handbooks. And, most of the time, a pocket knife is not considered a weapon, or is ignored. BUT, its in there, and they can enforce it, and be within the law doing so.
think of it like this, if you go "postal" and gun down 23 fellow employees with an office stapler, they are responsible, and will get sued. You have (OMG) GUNS!!!!! Of course they are going to be paranoid. And the fact that some other scaredy cat reported it to management makes them TOTALLY responsible, if they do nothing. Its a sad world these days.