Allow them in, but if they have to recognize this is a Nats board, we root for the Nats, and will throw shots at the Cards as part of it. If they want to post about a player like Kozma, what he can hit, whether a pitcher is pitch to contact or avoids contact, then fine. If they want to post "nats fans are front runners / Harper stinks / so and so is [gay / foreign / minority / handicapped] then they can take that knuckle dragging to the principal of their elementary school, or we can report it to their college or employer.
^ If they are let in we (the mods) will need to use the warning system very liberally with anything resembling trolling and general asshattery.