Recreational group riding is a lot of fun and a great way to build riding skills. You will meet people and ride routes you may not otherwise know about. Some routes are safer with a group than solo. These are not "paceline" rides but with a recommended spacing of at least a bike length or two to allow reaction time for road hazzards, braking and etc. Even though you may be able to go faster, it's unlikely you really have the skills to with the speed at full gas. One inept rider can bring down a group of riders with injuries which is probably what the "hot shots" were worried about. If it was just their ego's they probably would not be polite. Our club allows and welcomes ebikes on the moderate and slower ride groups.
Well said, and now that I've been riding the ebikes for a couple seasons, I always stay in the middle or back of the pack. Those people are way more fun. They talk more instead of the leaders who are deprived of oxygen from their aggressive pace.