So, cutting in line is rude. And I think the OP was ok to say something to the cutter.
BUT, I don't necessarily disagree with the Pharmacy for catering to the impatient customer. Yes, it sucks to see a rude person get their way, but in the long run, I think it's better for EVERYONE ELSE to identify somone (not the cashier) to get this customer out as quickly as possible. Otherwise, you have someone being disruptive for several minutes and slowing things down even more. Not to mention agitating everyone else around them. I understand that catering to rudeness does not necessarily encourage a rude person from behaving better in the future. I just don't think that it's up to a business, that needs to consider all their customers, to teach/enforce those lessons. This wasn't the time/place for it. I think the Pharmacy did the best they could given the circumstances.