“That is such a dumb OP. Just saying.
You cannot force anyone else to do something.”
He isn’t talking about forcing. Let’s say the OP was worded like this “Some stores that advertise as being tznius only, sell clothes that are only tznius when you wear a long-sleeve shirt underneath. Sometimes, they put these clothes on mannequins without the undershirt because it makes it look more appealing. Is this possibly maris ayin as it causes people the think the outfit is tznius without an undershirt?”
I wouldn’t make any kind of deal out of it either, but hey, it’s not the dumbest thread on the CR by any means.