Unfortunately too many of us really communicate like this with each other. We don't talk face to face or on the phone concerning hard issues, rather we take the easy way and simply shoot back and forth toxic emails.
If you got something hard or difficult to say, handle it biblically, with courage and in person, face to face (or over the phone if that's your only option).
And another ancillary point to be made from these signs- one of the common praises and affirmation we receive from people who come through our membership class is how impressed they are that we pray for other churches during our worship service. We pray for others because we want to have a Kingdom mentality and want God to bless others. And, unlike this parody of two churches feuding, we are not in competition with other churches. Consider praying specifically for a different church each week during your worship service.
Ok, let the battle begin (and have a good laugh in the meantime)!