They are public cameras taking pubic photos.
That's the whole deal with the "creepshots" deal on Reddit/Tumbler/etc. The subjects are in a public place. If someone does candid shots of lots of different types of people in a city and puts them in an art gallery, they're often considered art (even if 10% ~ 15% of the photos are of really pretty men or women that might be taken as being sexual). However, if you have a site that's only attractive men/women in public settings .. then it's not art ... or is it?
It all comes down to context. Legally it's fine to take public photos of people in many countries (and probably should be, because we don't want to go down that slope). Is it immoral? Well, that's another issue, and that depends on the context the photos were taken in. But you have to set a line somewhere, at least with the legal concerns. You might not like it, but it's just a part of being in a free society you have to deal with.
Now if someone takes a photo in a private area, like a bathroom or spying into a home, that's a different legal issue (unless it's looking up a skirt in Texas[1])
[1]: https://news.vice.com/article/court-ruling-makes-taking-pict...