BS”D
Dan lekaf zechus. First of all, if the guy is there to pick up medication, he obviously isn’t feeling too well (and you never know what medication it was – could be that R”L he has a mental disorder of some type). Second, some people cannot tolerate the kind of incompetence that is rife now ever since underskilled clerks and poorly programmed computers took over from highly trained pharmacists.
Funny you mention pharmacies. I have only been on the receiving end of abuse when I quietly shop in chain pharmacies while wearing my usual “charedi” (semi-Chassidish) levush. That includes SuperPharm in E”Y (but not the supposedly anti-Semitic European country in which I now live).