Yes they can !
I was stopped & searched by security who knew what an ILC camera was. I'd borrowed a Oly Pen & 40-150mm zoom lens for the recent Blondie gig @ Thetford Forest to get some shots but I had to take it back to the car & leave it there, accompanied by a security guy just in case !
Also printed on the tickets & gig info was a note saying no 'pro' style cameras with removable lenses would be allowed into the venue !