Honestly.....if I'm in line to use the bathroom and that handicap bathroom opens up, I'm using it unless.....
I see someone that obviously needs it
or
I see a mom with kids (I remember well how it is when you have kids that need to use the bathroom right at that moment)
People need to stay in their lane and not feel the need to police people every where they go. If I used a handicap stall, and someone scolded me like I was a child, I would just shake my head, wash my hands and leave. There's no way I'm giving them a response.
I would walk away too. People are crazy these days and I would not want to get into an argument. I think with social media being what it is, everyone feels they have the right to police everyone. Cameras will be whipped out and recording anyone doing anything perceived as wrong.