I'm the customer service side of the stage at our regular gig. On weekends we have security as it's a vantage point for most of the venue but in the past I've dealt with punters that want to talk mid song which usually results on a very wet ear, I will use the neck of my bass as a barrier. I have continued to play one handed whilst pushing people off the stage. I'm the event of punters invading during breaks I unleash a very angry sweary person. I've been doing this for 20 years and the nice approach rarely works. I bollock them like a small child. If they don't have the common sense or decency not to mess with the bands equipment then I show no mercy.
They have no idea how much the gear is worth.