If the hotel did not have any 120v outlets that were dedicated to a single 15/20 amp breaker, then absolutely they should deny your request to charge. You would be charging at 12 or 16 amps and if anything else plugged in on the same circuit, the breaker would likely trip. If their electricians installed the outlet poorly, a fire might even occur.
That being said, I've definitely successfully use 120v charging on a trip before. It wasn't necessary because there is a Supercharger a few miles away, but while we were at Disney in Orlando our resort had many 120v outlets and over the several days we were at the parks we were able to charge to 100% before we left and were able to drive directly to the Plantation, FL Supercharger 215 miles away instead of stopping at one of the 3 Superchargers along the way.
On the same trip on the way home we also plugged in to a 120v outlet in our hotel in Key Largo, FL which wasn't "necessary" but decreased our charging time on our way home.