So you're talking about "some men"? Who cares then. "Some men" do lots of things, most men do not.
If it is dangerous to reject someone, then there is something wrong with that person, not the app.
And this looks pretty much exactly like every other failed dating app, as every other dating app does.
EDIT: I really have no relevant opinion on the app. My concern here is the assumption of "if you're in public, you're mostly safe." It's not an untrue statement, but it is an incomplete picture. It's like saying "this chain is strong because 95% of these links are hardened steel."
Dating has risks because nobody can guarantee safety through the whole chain of events. It doesn't matter if it's safe in public, because what people overwhelmingly want out of dates is the eventuality of not being in public, and coordinating when and where that should happen, if at all, is difficult, and not a problem any app solves. (Regardless of whether they can or should solve it.)
The reason it matters in this particular context is because, in general, women do not think men are safe and dating apps must address this. To specifically counter your arguments about being in a public place with someone, that still opens the doors to: personally invasive touches when no one is looking, invasion of privacy (at this point some contact has occurred), and a physical knowledge of where you are, not to mention being in public hasn't necessarily helped: The murder of Kitty Genovese[1] comes to mind, as does most women having experienced being followed on the streets by men[2] a situation which isn't necessarily helped by public protectors[3] and if you must hear some stories themselves, here are some stories from reddit[4].
So, to answer your question, it is "okay" to operate under such an assumption because, in general, women feel unsafe around men, especially in the context of a dating app. Now, you could make the argument that women are illogical, or you could acknowledge that ~50% of the population might have some reason to feel that way. I personally prefer the latter, but if my opinion doesn't make a difference to you, I would recommend inquiring of women yourself, in some form or another.
[0]: https://www.quora.com/What-is-your-biggest-%E2%80%9CIve-neve...
[1]: https://en.wikipedia.org/wiki/Murder_of_Kitty_Genovese
[2]: http://www.stopstreetharassment.org/2010/01/75-percent-of-wo...
[3]: http://www.revelist.com/viral/portland-woman-stalking-office...
[4]: https://www.reddit.com/r/AskWomen/comments/3suj0m/ladies_wha...
If you're a woman and worried about that, maybe you shouldn't be randomly meeting men on the internet?
>As they say, the "crazy ex-girlfriend" will key your car, but the crazy ex-boyfriend will murder you.
Who says?
Do you stereotype other people in the same manner? Or just men?
>The murder of Kitty Genovese[1] comes to mind
You're going to use a brutal murder that occurred 50 years ago as an example of what women face today?
>here are some stories from reddit
Okay..now go read us some /r/MensRights stories.
The OP was about murder, so, no.