takahmamash: You made a statement that it is not my place to rebuke ANYONE unless I am a gabbai. This is simply not true. The mitzvah of rebuking sinners was given to every Jew, not just to gabbais.
I try my best not to look at immodest women. Sometimes I do want to go over to them, and tell the husband who is wearing a long kapote: “Take off your kapote and have your wife [who is wearing a mini-skirt] put it on.”