Ride out at the same time as they do and drop their asses.
+1. Then e-mail them back and say for a bunch of ROAD bikers they SUCK (or something to the equivalent), as a taste of their own e-mail etiquette. If they dont want to ride with you, thats cool but they dont have to be dorks about it either. My reaction, of course, is purely motivated by spite and my disdain for unwarranted condescension.