That we all conform to how society wants us to act, but given the choice and with no consequence most of us would probably say sod it and go on a rampage. (people are pretty selfish in general)
Hidden animalistic urges and all that stuff.
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MIKE: I've got it! Peter Cushing! We've got to drive a stake through his heart!
VYVYAN: Great! I'll get the car!
NEIL: I'll get a cushion.