I’m not sure why this is such an issue.
I see Jewish guys dressed like Yeshiva guys in places where jeans and a t-shirt are more appropriate, but I don’t think they should lower their “standards” to dress that way just because others do.
Now, I personally may not believe that dressing in black and white and hat makes a person more religious (I don’t think it matters where the dress originated from, it’s the message that it sends to everybody else when Yeshiva guys dress a certain way…)but I do believe that if a person feels that his dressing this way makes them a better person, then all the power to them.
Maybe this is what keeps them mentally religous? Maybe this is their way of reminding themselves that they represent Jews and they must act a certain way in public?
It may make us hot looking at them dressed in this way, but it’s their life and their choices.
I wouldn’t worrry so much about a Chilul Hashem, as long as their behavior is appropriate.