I have to say that I mostly agree with you. My mother always told me to take all I want but to eat all I take.
I go to an all you can eat buffet about once every year. There is always someone in there who eats enormous quantities of food. I am sure that these places take these eaters into account as a cost of doing business. I also always see others who eat only a very small amount. Then there are folks like me who eat a reasonable amount and are moderately pudgy. Either way, it costs the same.
To me, “all you can eat” means just that!
Bon appetit!
Surcharging them after the fact wasn't cool but informing them up front that their behavior was excessive and they could either leave now or pay a surcharge would be perfectly proper.
I'm also OK with taking a TINY portion of something new to sample and leaving it if you don't like it.