If it's not clearly similar to cycling protective gear, difficulties could arise at facilities where helmets are required such as military installations and some corporate campuses, in the sporadic jurisdictions that do require helmets (admittedly not a big issue for me), in parks and paths that require helmets, in group rides and organized events, and on those random occasions where you encounter someone who is ignorant of the facts and probabilities but who wants to make a point about cycling headgear.