It's a long time ago so it might not be the same 'that guy', maybe his dad.
We were playing at an Army training barracks, New Years Eve 1971 and there was a distinct lack of squaddies on the dance floor, (they were all in the bar) but there were plenty of girls and our singer was making conversation over the mic with one in particular that he fancied. Big mistake, especially when her BF came back from the bar and jumped on the stage to take a swing at the singer. Now our singer was sober, unlike the sqauddie and he neatly sidestepped the punch. This left the squaddie heading straight for our drummers brand new set of Ludwigs (his pride and joy). I prevented the collision with the drums by gently directing the guy off the stage by sticking the A and D machine heads of my Precision in his mouth and guiding him to the edge - backwards.
All hell broke loose, MPs appeared as if from nowhere and soon outnumbered the crowd. We were told to pack up and go but our van had been worked over before the MPs could protect it. We never played there again despite being offered the gig several times.