I'm really sorry that this happened. You should report it to the police, they may not catch them on this account, but should another incident happen, they can build a stronger case. Also, despite what bad press the police get, they do actually care and will keep a look out for the obvious dog, and or 1 or 2 males and if they do see them, they will stop and ask questions. There are some nasty people about and in ED we are Drawn into a bubble - these guys will get their Karma and based on their actions have probably had some already. Sorry your bubble got burst, but the massive majority of people are not like these twats.