I sit on the wing in L5, 4 rows back from the front and a couple of seats in from an aisle. At yesterday's game, there were 6 or 7 young blokes on the front row - very early twenties, if my old eyes can be trusted - supporting Port. They weren't particularly loud, definitely not aggressive or anti-social, but still drew close attention from a security bozzo in a yellow (or orange?) high-viz vest off and on, throughout the game.
His MI was to repeatedly stand, staring, hand on hips, in the aisle just behind their row, for minutes at a time. The young blokes clearly knew he was there, judging by how often they looked over their shoulders, to check if he was still around. They didn't seem so much intimidated (which I guess is what high viz man wanted) as thoroughly pissed off.
It occurred to me, watching them, that they had every right to feel angry and insulted at the inference that they were potential troublemakers, and if they'd reacted, it would have been a kind of self-fulfilling prophecy thing - expect trouble, go looking for it and you'll find it for sure.