You can hurt someone quite badly with a blunt instrument, but a touch extreme to confiscate them.
However, the gun thing I am 100% behind. I'm not going to tell the USA what to do, though you'll guess my stance I am sure, but the UK has strict gun control and even a toy gun can land you in serious trouble if it isn't obviously one. If you took a BB gun to a con here I'd not be overly polite about it, there's no need for it.