Don't be stupid. P2P refers to BitTorrent. The "we don't support it" thing should be taken literally - they will not give you support if you have trouble with it.
They are not referring to Demigod, and if they ARE doing something to hamper P2P... it will not affect Demigod, because it discriminates BitTorrent.
People on this forum should stop with their silly assumptions about ISPs and P2P. Use your head. P2P as in Demigod's context is few connections to other consumers. There is no way to block this unless you block all connections. P2P in BitTorrent's context is many connections to other consumers. BT connections also have a structure which, if your ISP is blocking P2P, will look for.
tl;dr You don't know what you're talking about, Virgin (or any other ISP, for that matter) don't block Demigod. Oh, and if you call your ISP and ask for support regarding Counter Strike or WC3, they'll also tell you they don't support it.