You really think that in this day and age? These members of staff have to deal with all sorts of people in their profession and I imagine top of their agenda is safety first.
There has been various articles about sections of fans high on coke/alcohol around the country so I can 100% understand why they take this course of action.
If it was a normal steward I would agree with you but they should be backed up by the police incase a situation arises.
