You give some good feedback but maybe you could have struck a stance of, "Hey, do you know you could be alienating a large fraction of your readers with the style of your job posting? Here is why."

These guys are trying to do a startup. It's a hard thing to do. Why grouse at them? Perhaps their posting is unprofessional because they are unprofessional, in the sense of not having had lots of professional experience yet. Maybe cut them some slack instead instead of increasing the concentration of venom in the commons.