I travel for work (airport inspections). Some may consider my camera a professional camera (Nikon 5600) with 3 quality lenses. I always take it inside. My truck was broken into once while at a hotel and I lost all my expensive inspection gear, thus, inside it goes. Besides, every night, I download the SD card on my PC. Of course I could simply bring in the SD card, but it seems safer to have the camera in the room.

NOW kids, pay attention. Last year, starting in March, I stayed in hotel rooms over 50 nights.

1. Take one of their nice white wash cloths and wipe down all hard surfaces with Lysol. Include door knobs, the desk and especially the handle/lever that raises & lowers the desk chair. Take a good look at the previously white cloth.

2. Then take photos of that "white" cloth with my professional camera for feedback & reviews. Housekeeping folks are not doing their jobs. Most places are pretty dirty.

Most of these hotels are IHG properties: Holiday Inn, Holiday Inn Express, Candlewood Suites, Staybridge, etc.

Perhaps that's why they don't want cameras on their properties.

No, it is not because they have their own photographers taking photo's. The reason you cannot take "professional" photo equipment into most basketball and baseball games is because a few bad ametuer photographers that used to sit in the stands and aim their long lenses over and around those in front of them. The masses of fans made such a fuss to management that very soon those camera's were banned. It is now common practice almost everywhere. You an thank the inappropriate operators of camera's for it.

I can understand the hotel not wanting photos taken of their private property, but not allowing a camera on the property is nuts.
You should email the corporate headquarters and tell them what happened. Be sure to name the manager and tell them how much money you've spent at their hotel.
Also tell them that if they do have an anti-camera policy, you'll be sure to stay at another hotel the next time you're in town... and you'll tell all your friends on Facebook, Instagram, etc. about how you were treated.