A Jumbo is one of those military-style bags, isn't it? If you were profiled as a trouble-maker, I doubt you could claim sexual discrimination. Legally I don't think you have a leg to stand on, so if you take it further you probably should be very, very polite about it.

Personally I like to be discrete and low-profile. I don't want stuff I carry to be upsetting movie theatre staff; that's not what I'm about.