A case of anti speedo prejudice

[Torchwatch]

Unless it is your intention to be arrested then being arrested will spoil your day, so when depending upon the discretion of security officers in public places it is best to treat them like the frog in a saucepan. Dropping a frog into a saucepan of hot water will cause it to immediately jump out, however if you put him in cold water and slowly heat it he will be content and allow himself to be cooked.
So if many in the crowd are wearing shorts (above the knee) then you can wear short shorts. If more guys start wearing short shorts then you can wear running shorts, as running shorts become popular then you could risk a square cut swim suit and finally speedos. Similarly men will wear tee shirts, running vests and then go topless if the weather is warm enough. The security officer will have no problem if "everybody" is doing it.
The security officer seeing one man in speedos in a crowd of the fully dressed will feel as threatened as the frog dropped in hot water and feel compelled to react, they are looking for something liable to cause a breach of the peace or a riot, and all security officers at sports events are afraid of streakers on the pitch during their watch.