What model and year, how many miles, stock or modified?
It's not unusual for the idle on a stock Harley to be less than rock steady, due to the stock fuel and timing settings along with the basic design issues like uneven firing spacing of a common crankpin 45° V-Twin, shared intake, etc.. The question would become "how much variation is acceptable", and "at what point does the variation signal a possible problem".
As for your dealership person's comments, it sounds like you have a typical Harley dealer. To some everything is "normal" and "they all do that". It's much easier to blow that smoke up folk's skirts than it is to do a little checking and then explaining to the customer exactly what's going on. A good way to deal with such jerks is to insist they roll out a couple more bikes similar to yours and prove that they "all" do that. Some characteristics people complain about are indeed normal, but I've found that many of the things typical dealerships blow off are not acceptable or necessarily even normal. Even some things that are normal (common) aren't necessarily acceptable, if you know what I mean. Oil leaks were normal (common) on 2007 CVO110 engines for instance, but that didn't make them acceptable. If you have another dealership nearby, or a good independent shop, get a second opinion.
Jerry