Freedom of speech exists in the public, not private spheres.

In this case, apps such as Titstare being presented at an event (aimed at all ages), such as this, only reinforce the perception that such events are boys clubs for 18-35 year old guys who like staring at tits. Presumably, you want that image to change: isn't it worth imposing restrictions to reduce the amount of "offence" caused to people in order to bring this about?