http://www.mirror.co.uk/news/uk-news/world-naked-bike-ride-nude-5796919

From the article : "In a response to complaints posted on Facebook, ride organiser Barry Freeman said: "We do not accept this behaviour and he was dealt with and removed before the ride started.""

I thought getting an erection is an involuntary response and can also happen spontaneously without the need for external arousal. How is this deemed 'bad behaviour', or indeed behaviour of any kind at all?