Asked to leave a restaurant

We were asked to leave a restuarant after Bobby (who is 4 and autistic) was having a meltdown after the starters were served. By that I mean crying loudly. A server told us that customers were complaining and they wanted us to leave. I said he would calm down and we would not leave. Then a female server came up and we were asked if we prefer to have our main course takeaway. I said no that he is autistic and would calm down. She shrugged her shoulders. Bobby was very upset and with the unfriendly environment we decided to talk to the staff. We went downstairs and found that the customers were 4 people (small resturant but but no means full). We told the manager that this was discrimination. Told the customers that there are a lot of autistic children and that needed to be more understanding. We were asked by the managers not to speak to the customers. We just left. I am so angry right now. Are they allowed to do this??