Oxy2D hosts some very popular servers and some kids out there cannot deal with this fact, so what they do is crash the servers so people join their shitty ones (Which doesn't seem to happen as the servers keep on getting crashed).
I've had servers I administrate crashed as well, I understand it is very frustrating and annoying to see that they can just get away with it. Eventually (Yes, eventually, not instantly) they will get bored. If they join your server, ban them. If they crash your server, wait a few minutes until you restart it.
They might have no life but they cannot stare at the CS2D serverlist all day. - This is probably the best advise you can take, although you can send IPs to SD and he can block them so all packets (Or whatever) that get sent will be ignored.