He was probably covering his a**. You don't know who is coming into your house to "look" at it, nor are background checks run beforehand. Do you want the possibility of a child molester or wannabe thug know which houses have firearms and that the house is open for a walk-thru? There are criminals who use the ruse of buying a home to scope it out for later shopping. When your house has a "for sale" sign on it, your neighbors get used to unknown cars and people at your home, would be buyers get to see your security setup, and a mental floorplan of your home.

I wouldn't get offended, just cover up your safe and gear with a blanket or something.