The point here is not obvious. What were they doing wrong? Yes, they were walking immodestly in a line in such a manner as to cause others to look at them, which is done anyways, and they were wearing immodest clothing, which is done anyways. Who is worse, the person who sings shabbos songs in shul with immodest people and calls it a fashion show, or the person who sings shabbos songs with the same thing and calls it maariv? My intuition says, "they are outright making it a fashion show, while other places this happens people bend the rules", but what's worse: a fool or a phony?